Logistics Service NexGate — Commerce, Location & Logistics Master Guide Purpose. This is the single reference for how buying, location and shipping work in NexGate. It captures every decision made so far and the reasoning behind each one, so that any implementer (human or Claude Code) can build from it, and future-you remembers why . Companion file: location-service-spec.md is the detailed build spec for the Location Service. This guide is the wider picture; that spec is the first thing to build. Guiding rule for everything here: simple over clever. No approval workflows, no features nobody asked for, no machinery a solo developer can't maintain. Where a simpler rule does the job, it wins. 0. The idea in one picture NexGate is a social-commerce super app: users open shops to sell and delivery businesses to ship, and buyers order and get goods delivered or collect them. NexGate never owns stock or vehicles — it connects the three sides and holds the money safely in between. ┌──────────────┐ browse / order / pay ┌──────────────┐ │ BUYER │ ───────────────────────────► │ NexGate │ └──────────────┘ ◄─────────────────────────── │ (platform) │ ▲ collect / receive + confirm (code) │ + escrow │ │ └──────┬───────┘ │ recommends & books │ │ ┌─────────┴─────────┐ ┌────────────┴───────────┐ │ SHOP (seller) │ hand over + code │ DELIVERY BUSINESS │ │ items, location │ ─────────────────────► │ (shipper) moves goods │ └───────────────────┘ └────────────────────────┘ Money path: Buyer → escrow → (on delivery code) → seller wallet + shipper wallet + NexGate fee Everything in this guide hangs off two services: Location Service — where things are. The foundation. Built first. Shipping Service — how goods move. Built on top of Location. 1. Core principles (apply everywhere) The pin (lat/lng) is the single source of truth for any place. Text is only a label. Location is collected only for a stated reason , never on app open, never as background tracking. The administrative hierarchy (region/district/ward) comes from NexGate's own data , computed from official NBS ward boundaries. Google is used only on the client for the map, place search and the live label — never called from the backend, never stored. Orders freeze a copy of every address and price. Later edits never change a past order. Users own businesses; businesses earn into the owner's one wallet. Shops sell, delivery businesses ship. Same ownership model for both. Money is held in escrow and released on a delivery code. Proof of handover, not trust. One shipment = one pickup (one shop) → one shipper → one drop-off. No multi-stop. Accept orders 24/7; be honest about timing. Closed hours delay the work, never the sale. Shippers describe their own pricing and coverage. NexGate never forces a pricing model. Trust is automatic, not a manual queue — phone verify, limits that grow with good history, ratings, and auto-pause on repeated failure. 2. Location Service (foundation) Full build detail is in location-service-spec.md . This is the summary. 2.1 What it owns Tanzania ward boundaries (NBS 2022) and pin → region / district / ward resolution Shop locations (one per shop, mandatory to publish) Buyer saved addresses (many, optional) and recent locations Order address snapshots (frozen copies) Stations and future zones (same shape-based pattern) Privacy rules for who sees which part of a location 2.2 How a pin becomes a place 📍 confirmed pin (lat, lng) / \ NBS ward shapes (ours) Google (client only) region, district, ward, codes "Mlimani City, Sinza Mori…" │ │ STORED (truth) shown while placing the pin only (never sent to backend, never stored) The lookup is a point-in-polygon test in PostGIS: which ward shape contains this point? It runs in milliseconds thanks to a spatial (GIST) index. If no ward contains the pin (beaches, lakes, borders), fall back to the nearest ward within 500 m ; beyond that, the pin is "outside coverage". 2.3 The ward data (done) Source: NBS 2022 Population & Housing Census — Tanzania Wards shapefile (official, ~3 m accuracy). Already converted to GeoJSON WGS84 (EPSG:4326) , geometries repaired, delivered as tz_wards_2022.geojson.gz . 4,344 wards, 31 regions. Primary key is ward_id (1–4344) because NBS codes are not unique. Loaded by a startup seeder (no Flyway, no version tracking) into PostgreSQL + PostGIS. The data file lives outside Git ( data/geo/ , mounted read-only into the container). District and region need no separate data. Every ward row already carries its council, district and region names + codes, so one pin lookup returns all levels at once. Coverage checks and reports just use the stored codes. The only case needing a district/region shape is drawing an outline on a map — build it on demand by dissolving wards ( ST_Union(geom) GROUP BY reg_code[, dist_code] ), never store a second dataset. 2.4 Address capture UX (same pin screen everywhere) Never ask for location on app open. Ask only when the user taps "Use my location". Fixed centre pin, the map moves under it (Bolt/Uber pattern). Satellite toggle. Accuracy circle. Confirm disabled until zoomed to street level. Search only moves the map, never confirms. Shop: pin + landmark + phone required (+ optional building, official address, photo). Mandatory. Buyer: pin + optional rider note only. Pin-only, Bolt style. Saving is optional; many saved addresses, plus recents. 3. Shipping Service (built on Location) 3.1 The whole shipping picture ┌───────────────────────────────┐ │ RECOMMENDATION ENGINE │ order (items, value, │ 1. read situation │ ranked options: pickup+dropoff wards, │ 2. gather eligible shippers │ 💰 Cheapest bulky?) ──────────────►│ 3. filter (coverage/limits) │──►⚡ Fastest │ 4. price each │ ⭐ Recommended │ 5. rank & label │ └───────────────┬────────────────┘ │ one standard contract per shipper: │ covers? · quote · book · cancel · status ┌────────────────────┼─────────────────────┐ ▼ ▼ ┌───────────────────┐ ┌───────────────────────┐ │ NATIVE shipper │ │ INTEGRATED shipper │ │ (NexGate business)│ │ (external API) │ │ tables + app/SMS │ │ Bolt, DHL… adapters │ └───────────────────┘ └───────────────────────┘ 3.2 Two classifications of every shipper A shipper is described by two independent fields : A. Service type — how goods move Type How it works Coverage set by Examples 🚪 Door-to-door Picks up at seller, delivers to buyer Areas (ward/district/region, or nationwide) + optional max distance Boda groups, Kibuti Express, DHL / EMS (wide area) 🚌 Station Seller drops at a station, buyer collects at a station Stations (pins) + lanes between them Bus companies, truck offices "Local" vs "intercity" is not a separate type — it falls out of how wide the area is. DHL is just door-to-door with a nationwide area. B. Connection — how NexGate talks to them Native (NexGate business) Integrated (external API) Set up by The owner, in the app NexGate, once, in code + admin Pricing Owner's tables Live from their API Jobs arrive App notification + SMS/WhatsApp link NexGate calls their API Status Owner taps buttons / link Their webhooks or polling → mapped Money Into owner's NexGate wallet NexGate pays them; they invoice NexGate New one Zero code (user signs up) One adapter per company They combine freely: a native door-to-door rider, a native station bus, integrated Bolt, integrated DHL. 3.3 One standard contract (why the engine never changes) Every shipper, native or integrated, answers the same five questions. That's all the engine knows: boolean covers(pickupWard, dropoffWard); // area / lane check Quote quote(order); // price + ETA Booking book(order); // returns a reference void cancel(ref); Status status(ref); // mapped to NexGate statuses Native answers from the owner's tables and app/link updates. Integrated answers by calling the company's API. Standard status ladder (every provider's own statuses are translated into this, so the buyer's tracking screen never changes): CREATED → BOOKED → PICKED_UP → IN_TRANSIT → AT_STATION → OUT_FOR_DELIVERY → DELIVERED ↘ FAILED / CANCELLED / RETURNED 3.4 Adding a provider = data, not code (for native) ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ Add delivery business ┆ Name: Shabiby Bus Parcels ┆ Type: ○ Door-to-door ● Station ┆ Connect: ● Native ○ Integrated (API) ┆ Contact: +255 7XX… (booking line) ┆ ───────────────────────────────────── ┆ Coverage ┆ Door-to-door → pick areas ┆ Station → add stations + lanes ┆ Pricing method (§3.6) ┆ Limits: max distance / max value ┆ Bulky: ○ No ● Yes (+extra) ┆ Settlement: ● Wallet ○ Pay at station ┆ [ ] Enabled ┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ Integrated providers (Bolt, DHL) enter nothing here; their adapter handles it. 3.5 Coverage: picked from what the system already knows Door-to-door → areas (from the region → district → ward list, or nationwide): Mbeya Riders 🚪 area: Mbeya district → local only Kibuti Express 🚪 area: Dar + Pwani → regional DHL / EMS 🚪 area: nationwide → intercity door-to-door Offered only when both pickup and drop-off pins fall inside its area. Station → stations + lanes (each station is a pin resolved to a ward, like a shop): Shabiby Bus 🚌 Stations: Mbeya Stand · Magufuli Terminal (Dar) · Dodoma Terminal Lanes: Mbeya ↔ Dar · Mbeya ↔ Dodoma Offered when it has a station near pickup and near drop-off. Buyer sees nearest stations first. Optionally a station shipper also delivers to the door around a station (then it also picks areas). Routes with multiple stops on the way. A bus line usually stops at several towns in order (Mbeya → Iringa → Morogoro → Dar). The shipper enters one route = an ordered list of its stations , not every pair of lanes. The system then treats any earlier stop → any later stop on that route as a valid trip (both directions if the route runs both ways): Route "Mbeya–Dar daily" (both ways) 1. Mbeya Stand 2. Iringa Office 3. Morogoro Stand 4. Magufuli (Dar) → valid trips: Mbeya→Iringa, Mbeya→Morogoro, Mbeya→Dar, Iringa→Morogoro, Iringa→Dar, Morogoro→Dar (+ reverses) 4 stops → all pairs auto-derived. Add a 5th stop and its new pairs appear at once. Pricing along a route (shipper's choice): A. Per segment, summed — one price per gap between neighbours; a longer trip is the sum ( Mbeya→Dar = Mbeya→Iringa + Iringa→Moro + Moro→Dar ). Simplest to keep accurate. B. Stop-to-stop table — a full price per pair, when it isn't a clean sum (e.g. a long-haul discount). Plus the usual value add-on (insurance) and bulky extra. First/last mile to a buyer not near a stop is added as a separate local door-to-door leg, each with its own code — unchanged. A lane is just the special case of a route with two stops. Model everything as routes. 3.6 Pricing — the shipper chooses the model, NexGate never forces one At registration the shipper picks one method: How do you charge? ○ Flat price ○ By distance (bands: 0–3 km, 3–7 km, …) ○ By package value (ladder: insurance — the shipper carries the risk) ○ By distance + value (added together) ○ Combined table (distance × value grid, each cell a full price) Plus, on top: bulky extra (if accepted), max distance and max value (filters, only when set). Why value-based for parcels: the shipper holds the insurance, so charging by the goods' value is fair, and "max accepted value" caps their risk. Quantity is handled for free — more items means a higher order value. Distance is measured from the two pins: start with straight-line × 1.3 (free, instant), switch to a routing service later if needed without changing shipper tables. Examples (5 km trip, phone worth 800,000): Mbeya Riders distance only 3,500 Shabiby (lane) value only 20,000 Kariakoo courier distance + value 3,500 + 3,000 = 6,500 Combined table (3–7km × 500k–2M) 7,000 Small rider flat 3,000 3.7 Package info — minimal No size or weight. Only: Order value — from the cart, automatic. Bulky? (yes/no) — one checkbox on the product (category can pre-tick furniture, fridges). Shippers that don't accept bulky are filtered out. A fridge never gets offered a motorbike. Vehicle type is not needed — "bulky vs not" is the only decision it would inform. Shippers may add a vehicle badge for display only (e.g. "Boda", "Pickup"); it drives no logic. Integrated providers (Bolt) pick the vehicle category inside their adapter. Mismatch rule: if the real package differs (bulky not ticked), the extra cost is the seller's (they chose), the buyer's price never changes after payment, and repeated mismatches auto-correct the product's bulky flag. 3.8 Who enters what Party At setup (once) Per order Seller Shop location, landmark, phone [ ] Bulky (usually none); tap "Ready for pickup" Shipper Coverage + one pricing method + limits + bulky Tap link; update status Buyer — Pick a delivery pin; tap one option (Cheapest/Fastest/Recommended) The system works out the rest: value, bulky, pickup+drop-off wards, eligible shippers, price, ranking. 3.9 The recommendation engine, step by step 1. WHERE pickup ward + drop-off ward → same district / same region / different region 2. WHO shippers whose coverage (areas / lanes) includes both wards + build station + door-to-door combinations where needed 3. FILTER drop any that fail a hard rule: area/lane not covered · over max distance · over max value · bulky needed but not accepted · closed & past cut-off (→ ETA shifts, not dropped) · provider currently auto-paused (repeated failures) 4. PRICE live quote (integrated) or the shipper's table (native) 5. RANK score by price · speed · reliability(history); weight by situation (urgent → speed; cheap item → price; expensive → reliability) label 💰 Cheapest / ⚡ Fastest / ⭐ Recommended; drop absurd outliers Backup: if the chosen shipper fails (no pickup, cancels), auto-offer the next best and tell the buyer. Reliability needs history , so at launch show only Cheapest and Fastest ; add Recommended once real delivery data exists. Reliability is your long-term moat — competitors can copy features, not your data. 3.10 Shipper onboarding: register → KYC → go live Shippers handle other people's goods and money, so onboarding has three parts. KYC gates going live , not filling the form — let them build the profile, then verify to switch on. Trust then grows automatically; no manual approval queue except on a flagged exception. Register (6-step form) → KYC verify → GO LIVE (low limit) → limits & badge grow with history Registration form (a short wizard, save-as-draft, admin can fill it for offline shippers): Step Fields Feeds the engine as 1 Basics name · service type (DOOR/STATION) · booking phone · WhatsApp? · logo identity, notify, branches next step 2 Coverage DOOR: areas (region/district/ward) or radius-from-base · STATION: stations + routes coverage check 3 Pricing method (flat/distance/value/dist+value/grid; route segment or table) · bulky yes/no (+extra) quote 4 Limits & alerts max value · max distance · won't-carry list · response window (default 30 min) · advance heads-up (default ON) filters , job alerts (§4.3a) 5 Hours & money opening hours + cut-off · settlement (wallet / pay-at-station) · payout account ETA/availability , money routing 6 Verify phone OTP · agree shipper terms (liability up to declared value) go live Minimum to go live = steps 1–3; steps 4–5 have working defaults; step 6 is just verify. A one-man rider finishes in ~2 min; a bus company takes longer only because it adds stations. KYC — fast, tiered, mostly automatic: Tier 0 phone verified → register, build profile (not live) Tier 1 + NIDA + ID photo + selfie match → GO LIVE, low max value (e.g. 200,000/order) Tier 2 + payout name matches NIDA → higher limit Tier 3 good history (N jobs, rating, low failures) → higher limit + "Verified" badge Auto-checks first (OTP, face-match selfie↔ID, name-match payout↔NIDA). Pass → live, no human. The mobile-money number is itself a KYC signal (already tied to a real NIDA in TZ). Manual review only on a flag (blurry ID, mismatch) — a small queue, not every shipper. Sellers get a lighter version of the same module (phone + NIDA + payout match before first payout). Licences & compliance — collect now, confirm mandatory ones with a professional later. Store each as document type + file + expiry . Mark required/optional per shipper type & tier once advised. Non-blocking at launch; uploading the real ones earns a "Verified business" badge. Group Documents (collect if the shipper has them) Identity & business NIDA · TIN (TRA) · BRELA (business name / company) · local-govt business licence · VAT (VRN) if over threshold Transport / courier LATRA licence (road carriage of goods/passengers — replaced SUMATRA) · TCRA courier/postal licence (door-to-door couriers) · TASAC (if freight-forwarding) Vehicle & driver (own fleet) vehicle registration · commercial/PSV licence · motor insurance (+ goods-in-transit) · driving licence · inspection/fitness Employees (if any) NSSF · WCF · OSHA Money / insurance mobile-money/bank payout · goods-in-transit / cargo insurance ⚖️ Flag (not legal advice): which licences are legally mandatory — especially LATRA for goods carriage and TCRA for courier services — and NexGate's own liability as the connecting platform, plus KYC/AML and escrow rules (Bank of Tanzania), must be confirmed with a Tanzanian lawyer / compliance professional. See §8. 4. Order & money flow 4.1 Checkout — pickup or delivery, per shop Each shop in the cart is its own shipment, so the choice is per shop: ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ Deliver to: 🏠 Home, Mbezi Juu ┆ 🏪 Shop A · Kariakoo · 2 items ┆ ○ Pickup at shop Free ┆ ● Delivery 🚪 Kibuti Express 4,000 ▾ ┆ 🏪 Shop B · Sinza · 1 item ┆ ● Pickup at shop Free ┆ ○ Delivery ┆ 🏪 Shop C · Mbeya · 1 item ┆ ● Delivery 🚌 Shabiby 20,000 ▾ ┆ ─────────────────────────────────────┆ Delivery total (2 deliveries) 24,000 └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ One shipment = one shop → one shipper → one drop-off. No multi-stop, ever. A 3-shop cart = 3 shipments, each with its own shipper, price, codes and escrow release. Pickup also uses escrow + a code (buyer shows code at the shop; seller enters it). 4.2 Escrow + delivery codes (proof of handover) sequenceDiagram actor Buyer participant NexGate as NexGate (escrow) participant Seller participant Shipper Buyer->>NexGate: pay (item + delivery) Note over NexGate: funds held in escrow Seller->>Shipper: hand over + SELLER pickup code Shipper->>NexGate: enter pickup code (proves shipper has it) Shipper->>Buyer: deliver Buyer->>Shipper: give DELIVERY code Shipper->>NexGate: enter delivery code Note over NexGate: release: NexGate->>Seller: item price − commission NexGate->>Shipper: delivery fee − commission NexGate->>NexGate: commissions Code rules (decided): Pickup code (seller → shipper): proves the shipper received the parcel — matters if it's lost. Delivery code (buyer → shipper): releases the money. Station collection: buyer gives the code to station staff, who enter it. Same as door-to-door. Multi-leg trips (rider → bus → rider): each handover has its own code , so each leg is paid as soon as it's done — the first-mile rider isn't left waiting days for a small fee. Open decisions to finalise (see §8): buyer unreachable / forgets code; item wrong or damaged after code; return window; cancellation cost. 4.3 Switching pickup ↔ delivery after ordering Order placed as PICKUP → "Get it delivered instead" → pick drop-off pin → fresh delivery quotes (today's prices) → pay delivery fee only → into escrow → shipment created, seller notified Allowed until the buyer has collected. Order placed as DELIVERY → "Collect it myself" → allowed only BEFORE the shipper has picked it up → delivery fee refunded to the buyer 4.3a When the shipper is contacted — offer at "Ready", not before The seller has two separate actions , and the shipper is only offered the job at the second one: Order arrives → seller ACCEPTS (yes, I'll fulfil) ← shipper NOT contacted yet → seller PACKS → seller taps READY FOR PICKUP ← NOW the binding offer goes to the shipper Offering at Ready (not at Accept) means: no shipper rides over to wait while the shop packs; if the seller can't fulfil, the order dies before any shipper was bothered; and the ETA/response-window start from a real ready moment. Heads-up (optional, per-shipper setting — default ON, can be disabled). So shippers can plan without being booked early, NexGate sends a non-binding heads-up when the seller accepts/starts packing. It commits nothing and starts no timer: On seller accept/pack → Heads-up (no commitment): "Order coming from Sinza, ~15 min. Be ready?" On seller READY → Binding OFFER + response window (30 min) starts ← the one that counts The heads-up is a shipper preference : Advance heads-up [✓] (default on) . A shipper who finds it noisy turns it off and only sees the binding offer at Ready. Re-check at Ready: if packing ran long and the chosen shipper has since closed / passed cut-off , the engine re-evaluates at Ready — same shipper still open → offer it; otherwise fall into normal reassignment (§4.4). A slow pack never leaves the order stuck with an offline shipper. 4.4 Shipper rejects the job → auto-reassign A shipper can decline an offered shipment (too far, too busy, bulky they can't carry, value too high, closed). This must resolve cleanly, because it touches money. Two rules make it safe: Escrow holds two parts — item money and delivery money. A rejection only touches the delivery part. The item money stays held, and the seller never re-approves — their job ended at "ready". The buyer's agreed price is protected. The system can reassign silently only if it holds that price or beats it; a higher price needs the buyer's yes. The flow: Seller taps READY (§4.3a) → shipment OFFERED to chosen shipper (delivery fee held) → shipper has a response window (e.g. 30 min, or until they next open) ├─ ACCEPT → pickup (code) → normal flow └─ REJECT (reason) or TIMEOUT → that shipper's delivery fee released back in escrow → shipment = REASSIGNING, recompute options excluding rejecters flowchart TD A[Shipper rejects / times out] --> B{Next-best shipper?} B -- none --> C[Buyer: switch to pickup refund, or cancel full refund] B -- same price or cheaper --> D[Auto-book next · refund difference to wallet] D --> E[Notify buyer: new courier, same price · NO action needed] B -- costs more --> F[Delivery money to buyer wallet · show fresh options+prices] F --> G[Buyer picks one · pays difference from wallet] G --> H[New shipper acts] E --> H Same or cheaper → auto, buyer does nothing (just a notification). The system walks down the ranked list on its own — shipper 1 rejects → shipper 2 auto-assigned → acts, and so on. Dearer → buyer confirms the new price (pays the difference from wallet, or gets a refund). None left → buyer chooses pickup (delivery refunded) or cancel (full refund). Reason feeds reliability. Chronic rejecters sink in the rankings and can auto-pause. Loop guard: cap auto-reassign at ~3 tries (or the order's handover window); after that, hand it to the buyer so a shipment never spins forever. There is no repeated approval — the seller is out of it after "ready", and the buyer is pulled in only when the price would rise or nobody is left. Otherwise the system does the chasing. 5. Free shipping Two funders, same mechanism. The shipper is always paid in full ; the discount is covered by whoever offered it, deducted at escrow release. 5.1 Seller-funded (per shop or per product) ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ Free delivery (shop setting) ┆ [✓] Offer free delivery ┆ Where: ○ Within [5] km of shop ┆ ● Areas: Ubungo, Kinondoni ┆ When: order over [50,000] (opt.) ┆ I pay up to: [5,000] per delivery ┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ Product override: ● Use shop setting ○ Always free ○ Never free Uses your ward boundaries and pin distance to decide eligibility. The cheapest qualifying option becomes free; a faster choice costs the difference. The cap protects the seller (buyer pays the rest above it). In a mixed shipment, free only if every item qualifies. 5.2 NexGate-funded (campaigns) ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ Campaign: Free delivery Dar weekend ┆ Areas: Dar es Salaam · Dates: 10–12 Oct Min order: 30,000 · NexGate pays up to 3,000 ┆ Who: First order only · Shops: All ┆ Total budget: 2,000,000 → auto-stops └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ Stacking (seller first, then NexGate): delivery price 7,000 − seller pays (cap 4,000) −4,000 − NexGate pays (cap 3,000) −3,000 = buyer pays 0 A total budget auto-stops the campaign — no runaway cost. Each shipment records who paid what . 6. Opening hours & orders outside hours 6.1 Hours apply to three things Who Why Shops Pickup availability; when a shipper can collect Delivery businesses Offered as "today" only when working; else ETA shifts Stations Where buyers collect parcels (often different hours from the company) 6.2 Hours editor (same screen everywhere) Mon–Fri 08:00–13:00 · 14:00–18:00 ← several ranges per day (lunch break) Sat 09:00–15:00 Sun Closed Special days: 25 Dec Closed · 9 Dec 10:00–14:00 ← override weekly (holidays, Eid) [ ] Temporarily closed (one-tap pause) Same-day cut-off: 16:00 (shippers) ← after this, pickup = next opening All times EAT (UTC+3) . Overnight ranges (18:00–02:00) allowed. 6.3 Orders outside hours — accept 24/7, be honest Order at Fri 22:00, shop opens Sat 09:00 ○ Pickup → "Ready from Sat 09:00" ● Delivery → "Arrives Sat ~12:00–15:00" Rules: Always accept orders. Blocking a night buyer loses the sale. Seller notified at once, but timers start at opening. "Accept within 2h / ready within 24h" pauses while closed — a 22:00 order isn't overdue at 07:00. Shipper jobs are scheduled, sent at the shipper's opening (not midnight). Shipper may accept early. Handover time = first moment the shop AND shipper are both open (after "ready", before cut-off). ETA = handover + the shipper's normal delivery time, skipping their closed hours. Temporarily closed → seller chooses "still accept (ships when back)" or "stop orders (hide Buy)". Safety net: if the seller never acts within 24 opening hours → auto-cancel + refund from escrow. 7. What we learned from others (and what to copy / avoid) Topic Jumia / Glovo / Uber / Bolt do… NexGate decision Ordering when closed Pre-order / scheduled ✅ Accept 24/7, show real time Delivery choice Door vs pickup station, options with price+ETA ✅ Per shop, Cheapest/Fastest/Recommended Money safety Escrow + 4-digit code ✅ Have it Seller onboarding Heavy docs + approval queue ❌ Avoid — phone verify + auto-limits Surge pricing Uber/Bolt dynamic ❌ Avoid — shipper ladders are clearer Separate rider apps Yes ❌ Avoid — NexGate deals with the business, not riders To add from others (currently gaps): Problem-report window — buyer can report a problem within ~24h of delivery before escrow releases. Two-way ratings — rate the buyer too (bad address / no-show), so shippers aren't stuck with them. Cancellation policy with cost — who pays when a buyer cancels after the shipper collected. Late-handover consequence — feed seller late handovers into the same reliability score shippers have. Address quality nudges — already helped by pin + landmark + ward check. 8. Open decisions to finalise before building Shipping # Decision Suggested default 1 Buyer unreachable / forgets delivery code Shipper marks "Delivered, no code" + photo → buyer 48h to dispute → else auto-release 2 Item wrong/damaged after code Short report window (24h) before release, or code = final 3 Lost / damaged parcel Shipper liable up to declared value; refund from shipper wallet; pickup code shows who held it 4 Cash on delivery (COD) Prepaid only at launch ; add "accepts COD" per shipper later 5 Escrow legality Check with a lawyer / payment partner (BoT, National Payment Systems Act) — not legal advice 6 Cancellation cost Free before pickup; buyer bears shipper's cost after pickup 7 Bolt for parcels RESOLVED (confirmed with Bolt): no parcel/delivery API in Tanzania — passenger rides only. Bolt is out as a shipper; rely on native shippers. Bolt only relevant if NexGate later adds an in-app passenger-ride feature (separate from shipping). 8 Mandatory licences & platform liability Which of LATRA / TCRA / business licence etc. are required per shipper type, and NexGate's liability as connector — confirm with a Tanzanian lawyer / compliance pro (§3.10) 9 KYC / AML level How much identity NexGate must verify & keep for shippers and sellers holding escrowed money — confirm with payment partner / lawyer 9. Note on the Bolt Ride Booker API (reference) Confirmed with Bolt (Oct 2026): no parcel/delivery API in Tanzania — passenger rides only. So Bolt is not a NexGate shipper. This section is kept only for a possible future in-app passenger-ride feature (separate from shipping). Prime Stack already has a Bolt Business account (ride billing), which is not the same as Ride Booker API access. The API doc shared earlier is a reseller passenger-ride API, useful as a model for integrated providers but not a parcel API . Key facts if it's ever used (e.g. in-app rides): Auth: OAuth2 client credentials, 10-minute tokens, backend-only (never in the mobile app). fare_id is fragile: expires in 5 min, single-use, stops must match the estimate exactly. On INVALID_FARE_ID , re-estimate and retry. Tracking: poll ride every 10 s / driver every 1 s; webhooks live-only (not sandbox), send just ride_id / type / state , whitelist Bolt's 3 IPs. States aren't linear (can bounce SEARCHING ↔ DRIVER_ON_ROUTE); final price can change for 24h+. Doc quirks: garbled Cancel section, misspelled reseler destroy URL, Fare_id capitalised once. Before use: confirm Ride Booker is enabled for Tanzania, currency and payment setup (samples are Tallinn/EUR). For NexGate's parcel shipping, native shippers matter far more than Bolt. Treat any Bolt/DHL integration as one adapter behind the standard contract (§3.3). 10. Build order (roadmap) Phase 1 — Location Service ◄── START HERE (spec + data ready) Docker PostGIS · seeder · pin resolution · shop location · buyer addresses · snapshots Phase 2 — Native Door-to-door shipping, one city Delivery business type · coverage (areas) · one pricing method · bulky flag Escrow + pickup & delivery codes · prepaid only · status via app/SMS link Checkout: pickup/delivery per shop · Cheapest + Fastest only Phase 3 — Station shipping (intercity) Stations + lanes · multi-leg codes · collect-at-station Phase 4 — Recommendation engine grows Reliability scores from history → add "Recommended" Free shipping (seller + NexGate campaigns) · opening-hours scheduling Phase 5 — Integrated providers Integrated adapters behind the standard contract — e.g. DHL (confirm parcel APIs first). NOT Bolt: confirmed no parcel API in TZ (rides only). Cross-cutting (fold in as you go): two-way ratings, problem-report window, cancellation policy, late-handover scoring. Do first: sign up your own first shippers (a few boda groups + one bus company) in one city — recommendations are worthless with no shippers. 11. Data model sketch (shipping — for when you build it) Logical only. Follow the project's ID type, audit and error conventions. All areas/stations point to the ward / district / region codes from the Location Service — no new map data needed. delivery_businesses owner_user_id, name, service_type(DOOR|STATION), connection(NATIVE|INTEGRATED), adapter_name?, contact_phone, accepts_bulky, bulky_extra, max_distance?, max_value?, response_window_min(default 30), advance_headsup(default true), settlement(WALLET|PAY_AT_STATION), enabled, rating, reliability business_areas business_id → region/district/ward codes it serves (DOOR) business_stations business_id, name, pin(lat,lng), ward_id, phone, hours (STATION) business_routes business_id, name, both_ways (STATION) route_stops route_id, station_id, stop_order (ordered list) → valid trip = earlier stop_order → later stop_order on same route (a 2-stop route is just a "lane") pricing_rules business_id, method(FLAT|DISTANCE|VALUE|DIST_VALUE|GRID), bands/ladder/grid as JSON route_pricing route_id, mode(SEGMENT|TABLE), segment prices between neighbours, or stop-to-stop table (STATION) opening_hours owner_type(SHOP|BUSINESS|STATION), owner_id, weekly ranges, special_days, temp_closed, same_day_cutoff shipments order_id, shop_id, shipper_business_id, service_type, pickup_snapshot, dropoff_snapshot (frozen), price, who_pays(buyer/seller/nexgate split), status(OFFERED|ACCEPTED|REASSIGNING|PICKED_UP|IN_TRANSIT| AT_STATION|OUT_FOR_DELIVERY|DELIVERED|FAILED|CANCELLED), offer_expires_at, reassign_count, pickup_code, delivery_code, leg_no? shipment_offers shipment_id, business_id, state(OFFERED|ACCEPTED|REJECTED|TIMEOUT), reject_reason?, offered_at, responded_at (one row per attempt) shipment_legs shipment_id, from, to, provider, status, cost, code (multi-leg) escrow_holds order_id, item_amount, delivery_amount, state(HELD|RELEASED|REFUNDED), breakdown (two parts: item + delivery) campaigns areas, dates, min_order, cap_per_delivery, budget, audience, active 12. Worked examples (engine walk-throughs) Illustrative numbers only. Shows the 5-step engine (WHERE · WHO · FILTER · PRICE · RANK) end to end. Reminder of the rules: value → price + insurance , bulky → vehicle/who can carry , quantity flows into value by itself , hours & limits filter, area/route decides eligibility. The registered shippers (set up once — used by all examples) ① Mbezi Boda 🚪 DOOR · Native Areas: Kinondoni, Ubungo (Dar) Pricing: distance 0–3km 2,000 · 3–7km 3,500 · 7–15km 5,000 · max 15km Bulky: NO Hours: 07:00–20:00 ② Dar Cargo 🚪 DOOR · Native Areas: whole Dar es Salaam region Pricing: distance + value dist: 0–5km 4,000 · 5–15km 7,000 value add: >500k +2,000 Bulky: YES (+15,000, car) Hours: 08:00–18:00 ③ Shabiby Parcels 🚌 STATION · Native Route: Mbeya–Dar (both ways): Mbeya ▸ Iringa ▸ Morogoro ▸ Dar segment: Mbeya–Iringa 8k · Iringa–Moro 6k · Moro–Dar 7k value add: >1M +5,000 · Bulky: YES (+10,000) Hours: 06:00–19:00 ④ EMS Courier 🚪 DOOR · Native · nationwide Pricing: value ladder ≤200k 15k · ≤1M 25k · >1M 3% Bulky: YES (+5,000) Hours: 08:00–16:00 Mon–Fri A — small but many, same city 20 phone cases , Sinza (Ubungo) → Mbezi (Kinondoni). Value 120,000 , not bulky, ~6 km, Sun 14:00. 1 WHERE both in Dar region, ~6 km 2 WHO ① ✓ ② ✓ ③ ✗ (no Dar-local) ④ ✓ 3 FILTER value ok · not bulky · ④ CLOSED Sun ✗ → candidates ① ② 4 PRICE ① 6km = 3,500 ② 7,000 + value add 0 = 7,000 5 RANK 💰⚡ ① Mbezi Boda 3,500 ~40min · alt ② 7,000 Buyer sees: 🚪 Mbezi Boda — 3,500 · ~40 min . Quantity raised value, but it still fits a bike. B — one but large (bulky, cheap) 1 mattress , same shops. Value 85,000 , Bulky ticked , ~6 km, Sun 14:00. 2 WHO ① ② ④ cover area 3 FILTER BULKY required → ① NO ✗ · ④ closed Sun ✗ → only ② 4 PRICE ② 7,000 + value 0 + bulky 15,000 = 22,000 5 RANK ⭐ only: ② Dar Cargo (car) 22,000 Buyer sees: 🚪 Dar Cargo (car) — 22,000 . Cheap item, but bulky kept it off the bike. C — intercity, multi-stop route, first/last mile Laptop , shop in Mbeya → buyer in Morogoro town. Value 1,500,000 , not bulky, Mon 10:00. 1 WHERE different regions (intercity) 2 WHO ①② don't reach Mbeya ✗ · ③ route: Mbeya(1) before Morogoro(3) ✓ · ④ nationwide ✓ 3 FILTER value ok · not bulky · both open Mon 10:00 4 PRICE ③ Mbeya→Moro 8k+6k = 14,000 + value>1M 5,000 = 19,000 (collect at Morogoro Stand) ④ EMS >1M = 3% of 1.5M = 45,000 door-to-door 2–3 days 5 RANK 💰 ③ Shabiby 19,000 tomorrow · 📦 ④ EMS 45,000 to door 2–3 days Buyer sees two groups: 🚌 Collect at station Shabiby · Morogoro Stand (2 km) · tomorrow · 19,000 📦 To your door EMS · 2–3 days · 45,000 Route matched automatically; priced only the Mbeya→Morogoro segment, not the whole line. D — shipper rejects → auto-reassign (from §4.4) From A, buyer picked ① 3,500 . Seller "Ready" → offer ① → ① TIMEOUT (busy) → 3,500 back in escrow · REASSIGNING · exclude ① → next = ② 7,000 → DEARER than 3,500 → delivery money → buyer wallet, ask: "Mbezi Boda unavailable. Dar Cargo 7,000 (+3,500). Continue?" → buyer accepts → pays 3,500 from wallet → ② gets the job (if next were ≤3,500 → auto-assigned silently, no buyer action) E — mixed cart, two shops (two shipments) Cart: phone from Shop X (Kariakoo, Ilala, value 400k, not bulky) + blender from Shop Y (Mbezi, Ubungo, value 90k, not bulky). Buyer in Mikocheni (Kinondoni). Sat 11:00. One shipment per shop (§4.1), priced independently: Shipment 1 X Kariakoo → Mikocheni (~9 km) WHO ② (Dar region) ✓ · ① ✗ (Ilala not in its areas) PRICE ② 7,000 + value 0 = 7,000 Shipment 2 Y Mbezi → Mikocheni (~5 km) WHO ① ✓ (Ubungo+Kinondoni) · ② ✓ PRICE ① 3,500 (cheapest) · ② 4,000 Checkout shows: 🏪 Shop X · Dar Cargo 7,000 🏪 Shop Y · Mbezi Boda 3,500 Delivery total (2 deliveries) 10,500 Two shippers, two codes, two escrow releases. One slow shop never blocks the other. F — free shipping (seller + NexGate stacked) Shoes , Shop Z in Kinondoni → buyer in Kinondoni. Value 60,000 , ~4 km, Fri 15:00. Shop Z offers free delivery in Kinondoni, pays up to 4,000 . A NexGate weekend campaign in Dar pays up to 3,000 . Cheapest qualifying option: ① Mbezi Boda 4km = 3,500 − seller pays (cap 4,000) −3,500 → fully covered by seller − NexGate not needed = buyer pays 0 Shipment records: who_pays = seller 3,500 Buyer sees: 🚪 Free delivery · ~35 min (badge). Shipper still paid 3,500 in full from seller's earnings. If the trip were 9 km = 5,000: seller 4,000 + NexGate 1,000 = buyer still 0, split recorded. One-line summary Build the Location Service first (spec + data are ready). Then layer shipping on top: shippers are businesses with a wallet, described by service type × connection , answering one standard contract; they set their own coverage and pricing; money sits in escrow and releases on a delivery code; orders are accepted 24/7 with honest timing; and free shipping, hours and ratings slot into the same engine without changing it. NexGate Location Service — Implementation Spec For the implementer (Claude Code): read this whole file before writing code. Follow the existing conventions of the NexGate codebase (package layout, REST path style, auth/security, error format, ID type, DTO style, tests). Where this spec and the codebase conventions differ on style , follow the codebase. Where they differ on behaviour/rules , follow this spec. Keep it simple — no approval workflows, no extra services, no over-engineering. 0. Summary The Location Service is a module inside the existing Spring Boot backend (not a microservice). It owns everything about where things are: Tanzania ward boundaries (official NBS 2022 data) and pin → region/district/ward resolution Shop location (one per shop, mandatory before a shop can be published) Buyer saved addresses (many per buyer, optional) and recent locations Order address snapshots (frozen copy of pickup/drop-off for an order) Privacy rules for who may see which part of a location Shipping (providers, quotes, tracking) is out of scope — it will be built later on top of this service. 0.1 Where the Location Service is used across NexGate It is the shared foundation for every feature that cares about where . Build the two core calls — resolve(pin) → ward/district/region and areaMatch(areaSet, pin-or-area) → bool — as reusable functions, because all of these call them: Shop setup — the shop's mandatory pickup location (pin → ward). Buyer addresses & checkout — saved/recent delivery addresses; the delivery pin. Order snapshots — frozen pickup + drop-off for every order. Shipping — coverage (later) — is a trip inside a shipper's areas / route stops? Shipping — pricing (later) — pin-to-pin distance for distance-based fees. Shipping — trip type (later) — same district / same region / cross-region, from the two wards. Free-shipping zones (later) — seller or NexGate "free within these areas / X km of shop". "Near me" feed & search (later) — show shops/products by the viewer's rough area. Geo-targeted ads / boosting (later) — show a boosted post only in chosen areas, or only where the seller can deliver; match on the viewer's rough area only , aggregate counts, no tracking. Reports & analytics — group orders/activity by ward/district/region codes (never per person). Everything above reuses the same ward data and the same two functions — no new map work per feature. Only the two core calls are in scope now; the rest are listed so the API is designed to serve them. 1. Principles (non-negotiable) The pin (lat/lng) is the truth. Every saved location has a pin confirmed by the user on a map. No location is ever saved without coordinates. We take location only for a reason. No location request on app open, no background tracking for buyers or shops, no movement trails. Store only the pin the user confirmed . Hierarchy comes from our own data, not Google. Region/district/ward are computed on the backend from NBS ward shapes. Google is used only on the client (map display, place search, live label while placing the pin). The backend never calls Google and never stores Google text . Orders keep their own frozen copy of addresses. Editing or deleting a saved address never changes past orders. Simple. One module, plain SQL for spatial work, no Flyway, no version tracking, no JPA entity for the ward table. 2. Architecture ┌──────────────────────── CLIENTS (Android · iOS · Web) ────────────────────────┐ │ Pin screen: Google Map + Places search + live Google label (display only) │ │ Sends: confirmed lat/lng + user text (landmark/note/phone/label) │ └───────────────────────────────────────┬───────────────────────────────────────┘ │ REST ┌───────────────────────────────────────▼───────────────────────────────────────┐ │ NexGate Spring Boot backend │ │ │ │ ┌──────────────────────── location module ───────────────────────────────┐ │ │ │ WardResolver pin → ward/district/region (PostGIS query) │ │ │ │ LocationValidator coverage, nearest-ward snap, device-distance check │ │ │ │ UserAddressService saved addresses, default, duplicates, limits │ │ │ │ RecentLocationSvc last unsaved pins (max 5, 60 days) │ │ │ │ ShopLocationService one mandatory location per shop │ │ │ │ SnapshotFactory frozen AddressSnapshot for orders │ │ │ │ WardDataSeeder creates tables/indexes + loads ward file once │ │ │ └────────────────────────────────┬────────────────────────────────────────┘ │ │ │ (internal Java calls) │ │ ┌────────────── orders / checkout ─────────┐ ┌──── shipping (FUTURE) ────┐ │ │ │ stores AddressSnapshot on each order │──►│ reads snapshots only │ │ │ └───────────────────────────────────────────┘ └───────────────────────────┘ │ └───────────────────────────────────────┬───────────────────────────────────────┘ │ JDBC ┌───────────────────────────────────────▼───────────────────────────────────────┐ │ PostgreSQL + PostGIS (Docker image postgis/postgis) │ │ tz_wards · shop_locations · user_addresses · recent_locations │ └────────────────────────────────────────────────────────────────────────────────┘ Ward data file (NOT in Git): tz_wards_2022.geojson.gz → mounted read-only into app container Who decides what 📍 confirmed pin (lat, lng) / \ NBS ward shapes (ours, backend) Google (client only) region, district, ward, codes "Mlimani City, Sinza Mori…" │ │ STORED (truth) shown on pin screen only, never sent/stored 3. Ward data 3.1 Source National Bureau of Statistics (NBS) Tanzania — 2022 Population and Housing Census, Tanzania Wards (Shapefiles) . Already converted for us to GeoJSON, WGS84 lat/lng (EPSG:4326) , 21 self-intersecting shapes repaired. File: tz_wards_2022.geojson.gz (~6.7 MB gzipped, ~30 MB raw). 4,344 features. Attribution required somewhere in the app's legal/about page: "Ward boundaries © National Bureau of Statistics, Tanzania (2022 PHC)." 3.2 File format (what the seeder reads) { "type": "FeatureCollection", "crs": { "type": "name", "properties": { "name": "urn:ogc:def:crs:OGC:1.3:CRS84" } }, "features": [ { "type": "Feature", "properties": { "ward_id": 1, "nbs_code": "010111011", "reg_code": "01", "reg_name": "Dodoma", "dist_code": "01", "dist_name": "Kondoa", "counc_code": "11", "counc_name": "Halmashauri ya Wilaya ya Kondoa", "ward_code": "011", "ward_name": "Changaa" }, "geometry": { "type": "Polygon", "coordinates": [[[35.6782, -4.736511], ...]] } } ] } 3.3 Data facts the code must respect Fact Consequence Coordinates are [longitude, latitude] (GeoJSON order) ST_MakePoint(lng, lat) — longitude first. Most common bug. Geometry is a mix of Polygon and MultiPolygon Always store with ST_Multi(...) into a MultiPolygon column. ward_code alone is NOT unique; even nbs_code repeats for 5 wards (NBS data issue) ward_id (1..4344) is the primary key. nbs_code is informational, not unique. Shapes stop at shorelines (sea, Lake Victoria, etc.) Pins on beaches/jetties may fall outside every ward → nearest-ward fallback (§6). 31 regions, ~4,344 wards. Dar es Salaam has 5 councils (Ilala, Kinondoni, Temeke, Ubungo, Kigamboni) Expected counts for sanity tests. 3.4 District & region come from the ward rows — no separate files There is no separate district or region boundary table . Every ward row already carries its council, district and region names and codes, so a single ST_Contains lookup returns all levels at once: pin → ward (Kariakoo) → already has dist_name=Ilala, reg_name=Dar es Salaam, codes included Coverage checks ("shipper serves Dar es Salaam region") match reg_code / dist_code on the resolved ward — no shape needed. Reports group orders by the stored reg_code / dist_code . Drawing a district or region outline on a map (e.g. shipper coverage) is the only case that needs a shape. Build it on demand by dissolving wards — do NOT store a second dataset: -- district outlines (view or materialized view, optional) SELECT reg_code, reg_name, dist_code, dist_name, ST_Union(geom) AS geom FROM tz_wards GROUP BY reg_code, reg_name, dist_code, dist_name; -- region outlines SELECT reg_code, reg_name, ST_Union(geom) AS geom FROM tz_wards GROUP BY reg_code, reg_name; Use counc_code as well if councils (halmashauri) matter for coverage; the ward rows carry it too. 4. Infrastructure 4.1 Docker Database image must include PostGIS: use postgis/postgis:- with the same Postgres major version currently used (e.g. postgres:16 → postgis/postgis:16-3.4 ). Same major version keeps existing data volumes working. App container mounts the data folder read-only: services: db: image: postgis/postgis:16-3.4 # match current PG major version app: volumes: - /opt/nexgate/geo:/app/geo:ro # host folder holding tz_wards_2022.geojson.gz environment: GEO_WARDS_FILE: /app/geo/tz_wards_2022.geojson.gz Local dev: put the file in ./data/geo/ and add data/geo/ to .gitignore . Never commit the data file. 4.2 Config # path to .geojson or .geojson.gz ; empty/missing → seeder logs WARN and skips geo.wards-file=${GEO_WARDS_FILE:./data/geo/tz_wards_2022.geojson.gz} 4.3 No Flyway, no version tracking Schema for this module is created by the WardDataSeeder at startup using idempotent SQL ( IF NOT EXISTS ). It runs after Hibernate initialises (use ApplicationRunner or ApplicationReadyEvent ). tz_wards has no JPA entity (read via JdbcTemplate /native SQL only), so Hibernate never touches it. shop_locations , user_addresses , recent_locations may be JPA entities following project conventions, with plain lat / lng double columns (no hibernate-spatial needed). Spatial work is done in native SQL using ST_SetSRID(ST_MakePoint(lng, lat), 4326) . The seeder adds the spatial expression indexes afterwards. 5. Database 5.1 Entity relationships erDiagram TZ_WARDS ||--o{ SHOP_LOCATIONS : "resolved to" TZ_WARDS ||--o{ USER_ADDRESSES : "resolved to" TZ_WARDS ||--o{ RECENT_LOCATIONS : "resolved to" USERS ||--o{ USER_ADDRESSES : owns USERS ||--o{ RECENT_LOCATIONS : has SHOPS ||--|| SHOP_LOCATIONS : "has exactly one" ORDERS ||--|| ADDRESS_SNAPSHOT : "pickup (frozen copy)" ORDERS ||--|| ADDRESS_SNAPSHOT : "drop-off (frozen copy)" Addresses store ward_id and copies of the names/codes (denormalised) so reads never need a join and display stays stable. 5.2 tz_wards (created + filled by seeder) CREATE EXTENSION IF NOT EXISTS postgis; CREATE TABLE IF NOT EXISTS tz_wards ( ward_id INTEGER PRIMARY KEY, nbs_code VARCHAR(16) NOT NULL, reg_code VARCHAR(4) NOT NULL, reg_name VARCHAR(100) NOT NULL, dist_code VARCHAR(4) NOT NULL, dist_name VARCHAR(100) NOT NULL, counc_code VARCHAR(4) NOT NULL, counc_name VARCHAR(200) NOT NULL, ward_code VARCHAR(8) NOT NULL, ward_name VARCHAR(100) NOT NULL, geom geometry(MultiPolygon, 4326) NOT NULL ); CREATE INDEX IF NOT EXISTS idx_tz_wards_geom ON tz_wards USING GIST (geom); CREATE INDEX IF NOT EXISTS idx_tz_wards_names ON tz_wards (reg_name, dist_name, ward_name); 5.3 Location tables (logical schema — use project ID type & audit conventions) shop_locations — exactly one per shop column type rule id project ID type PK shop_id FK → shops unique lat, lng double required, rounded to 6 decimals ward_id int resolved by backend reg_name, dist_name, ward_name, nbs_code text copied from ward match_type enum CONTAINED / NEAREST from resolver landmark text (≤ 300) required ("Near Shekilango stop, above Vodashop, 1st floor") building text (≤ 100) optional ("Shop 12") pickup_phone text required , E.164 (+255…) official_address text (≤ 100) optional (Anwani za Makazi) photo_url text optional (shop front photo, uses existing media upload) created_at, updated_at timestamp user_addresses — buyer's saved addresses (0..10 per user) column type rule id project ID type PK user_id FK → users label_type enum HOME / WORK / OTHER HOME and WORK max one each per user custom_label text (≤ 40) required when OTHER ("Mama's place") lat, lng double required, 6 decimals ward_id, reg_name, dist_name, ward_name, nbs_code, match_type resolved by backend note text (≤ 300) optional note for rider ("Black gate, call on arrival") receiver_name text defaults to user's name receiver_phone text defaults to user's phone, E.164 is_default boolean at most one true per user last_used_at timestamp updated when used in an order created_at, updated_at timestamp recent_locations — unsaved delivery pins (max 5 per user, expire after 60 days) column type rule id project ID type PK user_id FK → users lat, lng, ward_id, reg_name, dist_name, ward_name, match_type as above note, receiver_name, receiver_phone as used in that order last_used_at timestamp Indexes created by seeder after Hibernate (idempotent): CREATE UNIQUE INDEX IF NOT EXISTS ux_shop_locations_shop ON shop_locations (shop_id); CREATE INDEX IF NOT EXISTS idx_shop_locations_geog ON shop_locations USING GIST ((ST_SetSRID(ST_MakePoint(lng, lat), 4326)::geography)); -- for future "near me" CREATE INDEX IF NOT EXISTS idx_user_addresses_user ON user_addresses (user_id); CREATE UNIQUE INDEX IF NOT EXISTS ux_user_addresses_default ON user_addresses (user_id) WHERE is_default; CREATE UNIQUE INDEX IF NOT EXISTS ux_user_addresses_home ON user_addresses (user_id) WHERE label_type = 'HOME'; CREATE UNIQUE INDEX IF NOT EXISTS ux_user_addresses_work ON user_addresses (user_id) WHERE label_type = 'WORK'; CREATE INDEX IF NOT EXISTS idx_recent_locations_user ON recent_locations (user_id, last_used_at DESC); (If the project creates these tables itself via its own mechanism, keep the indexes in the seeder anyway.) 5.4 AddressSnapshot (frozen copy stored on orders) Not a table owned by this module. The orders module stores it (e.g. a jsonb column pickup_snapshot / dropoff_snapshot , or embedded columns — follow project convention). Immutable once stored. { "lat": -6.774512, "lng": 39.241871, "wardId": 1131, "nbsCode": "070113062", "regionName": "Dar es Salaam", "districtName": "Kinondoni", "wardName": "Kijitonyama", "matchType": "CONTAINED", "label": "Home", // null if unsaved "landmarkOrNote": "Black gate, call on arrival", "building": null, "contactName": "Kibuti", "contactPhone": "+2557XXXXXXXX", "sourceType": "USER_ADDRESS", // USER_ADDRESS | NEW_PIN | SHOP_LOCATION "sourceId": "…", // id of saved address/shop location, null for NEW_PIN "capturedAt": "2026-10-08T12:30:00Z" } 6. Pin resolution (core algorithm) input: lat, lng │ ├─ basic checks: lat ∈ [-90,90], lng ∈ [-180,180], not (0,0) ── fail → 400 INVALID_COORDINATES │ ├─ round to 6 decimals │ ├─ Query A: ward whose shape CONTAINS the point │ found → matchType = CONTAINED, distanceM = 0 ───────────────────────► return ward │ ├─ Query B: nearest ward within 500 m (shoreline, beach, jetty, border gaps) │ found → matchType = NEAREST, distanceM = n ─────────────────────────► return ward │ └─ nothing → OUTSIDE_COVERAGE (sea, lake, outside Tanzania) -- Query A (uses GIST index) SELECT ward_id, nbs_code, reg_name, dist_name, counc_name, ward_name FROM tz_wards WHERE ST_Contains(geom, ST_SetSRID(ST_MakePoint(:lng, :lat), 4326)) LIMIT 1; -- Query B (only if A returns nothing) SELECT ward_id, nbs_code, reg_name, dist_name, counc_name, ward_name, ST_Distance(geom::geography, ST_SetSRID(ST_MakePoint(:lng, :lat), 4326)::geography) AS distance_m FROM tz_wards WHERE ST_DWithin(geom::geography, ST_SetSRID(ST_MakePoint(:lng, :lat), 4326)::geography, 500) ORDER BY distance_m LIMIT 1; Point exactly on a border → whichever ward Query A returns is fine. Constant: NEAREST_WARD_MAX_METERS = 500 . 6.1 Validation rules Check Applies to Result Invalid coordinates all block INVALID_COORDINATES No ward within 500 m all block OUTSIDE_COVERAGE ("We don't deliver here yet") Matched by NEAREST all allow, matchType=NEAREST (info only) Pin > 1 km from device position (client sends optional deviceLat/deviceLng ) shop only allow, return warning FAR_FROM_DEVICE with distance; client asks "Your pin is 3.2 km from where you are. Is this your shop?" Saved address within 50 m of another saved address of same user buyer save 409 NEAR_DUPLICATE with the existing address; client asks "This looks like 🏠 Home. Use it?"; client may resend with allowNearDuplicate=true More than 10 saved addresses buyer save block ADDRESS_LIMIT_REACHED Second HOME or WORK buyer save/edit block LABEL_ALREADY_USED Client-only checks (not backend): GPS accuracy circle, minimum zoom before confirm, satellite toggle. 7. Business rules 7.1 Shop location Exactly one location per shop. Required to publish a shop — expose hasLocation(shopId) for the shop module. Required fields: pin, landmark, pickup phone. Optional: building, official address, photo. Only the shop owner (and shop admins per existing roles) can set/edit it. No approval step. Editing affects future orders only (old orders keep snapshots). 7.2 Buyer addresses Saving is optional and the buyer's choice (checkbox "Save for next time"). Max 10 saved. HOME/WORK at most once each; OTHER needs a custom label. First saved address becomes default automatically. Buyer can change default. If the default is deleted → no default (client pre-selects most recently used). Receiver name/phone default to the buyer's profile; buyer can change ("someone else"). Edit = change pin (re-resolved), label, note, receiver. Delete = hard delete . 7.3 Recent locations When an order uses a new pin that was not saved , store it in recent_locations . Keep max 5 per user (delete oldest beyond 5 on insert). Ignore and delete entries older than 60 days (on read/insert — no scheduler needed). If the new pin is within 50 m of an existing recent, update that one's last_used_at instead of inserting. Buyer can delete one or clear all. A recent can be promoted to a saved address (client posts a normal create). 7.4 Orders / snapshots Checkout passes either addressId (saved), recentId , or a new pin payload. Location module returns an AddressSnapshot ; orders module stores it; snapshot never changes. Using a saved address updates its last_used_at . Pickup snapshot comes from the shop location ( sourceType=SHOP_LOCATION ). 7.5 Account deletion Deletes all user_addresses and recent_locations of that user. Order snapshots remain (order records). 8. Privacy & visibility Data Buyer Seller Rider / delivery provider Third parties Buyer saved addresses / recents own only ❌ ❌ ❌ Order drop-off area (ward, district, region) ✅ ✅ ✅ ❌ Order drop-off exact pin + note + phone ✅ only if seller delivers itself ( sellerDelivers=true ) ✅ for that shipment only ❌ Shop location (pin, landmark, ward) ✅ public ✅ ✅ ❌ Shop pickup phone after order ✅ ✅ ❌ Implement as two snapshot views: AddressSnapshotPublicView (area only) and AddressSnapshotFullView . Analytics/reports aggregate by ward/district only — never per person. Never log full coordinates together with user identifiers at INFO level. 9. REST API Paths shown as examples — adapt prefix/style/auth to the existing project. All endpoints require authentication except GET /shops/{id}/location (public view). 9.1 Resolve (used live by pin screen after the map stops moving — debounce ~400 ms client side) GET /api/v1/locations/resolve?lat=-6.8190&lng=39.2768 200 { "covered": true, "matchType": "CONTAINED", "distanceM": 0, "ward": { "wardId": 1146, "nbsCode": "070214112", "wardName": "Kariakoo", "districtName": "Ilala", "councilName": "Halmashauri ya Jiji la Dar es Salaam", "regionName": "Dar es Salaam" }, "areaLabel": "Kariakoo, Ilala, Dar es Salaam" } 200 { "covered": false, "reason": "OUTSIDE_COVERAGE" } Nothing is stored by this call. 9.2 Buyer addresses Method Path Notes GET /api/v1/me/addresses list, default first, then last_used_at desc POST /api/v1/me/addresses create (body below) PUT /api/v1/me/addresses/{id} update (same body) DELETE /api/v1/me/addresses/{id} hard delete POST /api/v1/me/addresses/{id}/default make default GET /api/v1/me/recent-locations max 5, ≤ 60 days DELETE /api/v1/me/recent-locations/{id} remove one DELETE /api/v1/me/recent-locations clear all POST /api/v1/me/addresses { "lat": -6.774512, "lng": 39.241871, "labelType": "OTHER", "customLabel": "Mama's place", "note": "Black gate, call on arrival", "receiverName": null, "receiverPhone": null, // null → use profile "makeDefault": false, "allowNearDuplicate": false } 9.3 Shop location Method Path Notes GET /api/v1/shops/{shopId}/location public view (no phone unless authorised) PUT /api/v1/shops/{shopId}/location create or replace; owner only PUT /api/v1/shops/{shopId}/location { "lat": -6.770901, "lng": 39.229410, "landmark": "Near Shekilango stop, above Vodashop, 1st floor", "building": "Shop 12", "pickupPhone": "+2557XXXXXXXX", "officialAddress": null, "photoUrl": null, "deviceLat": -6.7712, "deviceLng": 39.2291 } // optional, for FAR_FROM_DEVICE warning → 200 { ...location..., "warnings": [ { "code": "FAR_FROM_DEVICE", "distanceM": 3200 } ] } 9.4 Internal Java API (for orders/shop modules — not REST) ResolveResult resolve(double lat, double lng); boolean hasShopLocation(ShopId shopId); AddressSnapshot snapshotFromShop(ShopId shopId); AddressSnapshot snapshotFromAddress(UserId userId, AddressId addressId); // also bumps last_used_at AddressSnapshot snapshotFromRecent(UserId userId, RecentId recentId); AddressSnapshot snapshotFromNewPin(UserId userId, NewPinRequest req); // req.saveForLater → creates address, else records recent 9.5 Error codes INVALID_COORDINATES , OUTSIDE_COVERAGE , NEAR_DUPLICATE (409, includes existing address), ADDRESS_LIMIT_REACHED , LABEL_ALREADY_USED , SHOP_LOCATION_REQUIRED (thrown by shop publish), NOT_FOUND , FORBIDDEN . Use the project's existing error response format. 10. WardDataSeeder (startup) App starts (after Hibernate) │ ├─ 1. CREATE EXTENSION IF NOT EXISTS postgis (log clear error if not permitted) ├─ 2. CREATE TABLE IF NOT EXISTS tz_wards … + indexes ├─ 3. CREATE INDEX IF NOT EXISTS … on location tables (§5.3) │ ├─ 4. BEGIN; SELECT pg_advisory_xact_lock() ← only one container seeds │ SELECT count(*) FROM tz_wards │ ├─ > 0 → COMMIT, done (normal startup, instant) │ └─ = 0 → file exists? │ ├─ no → WARN "ward file not found at …; ward lookup disabled", COMMIT, continue startup │ └─ yes → stream features (Jackson streaming parser, gzip if *.gz) │ batch insert 200 rows: │ INSERT INTO tz_wards (…, geom) │ VALUES (…, ST_Multi(ST_SetSRID(ST_GeomFromGeoJSON(?), 4326))) │ ON CONFLICT (ward_id) DO NOTHING │ COMMIT; ANALYZE tz_wards │ log "Loaded N wards in X s" (expect 4344) │ └─ 5. If wards were just loaded AND user_addresses/shop_locations/recent_locations already have rows → re-resolve all of them (update ward_id + name copies + match_type). Order snapshots untouched. Rules: Stream the file — never load all 30 MB into memory. Accept both .geojson and .geojson.gz . Seeder failure must not crash the app; resolve endpoint then returns 503 WARD_DATA_UNAVAILABLE . Updating to new boundaries later: replace file on server, TRUNCATE tz_wards; , restart. Step 5 re-resolves saved locations. 11. Client behaviour (Android · iOS · Web) 11.1 Location permission Never ask on app open. Ask only when the user taps "Use my location" on the pin screen. Show our own explainer first; trigger the OS/browser prompt only if the user agrees. Foreground / "While using the app" only. Never background location for buyers or shops. Handle approximate location (Android 12+, iOS 14+): use it to centre the map, ask user to drag map to exact spot. iOS: purpose string e.g. "NexGate uses your location to set your shop or delivery address faster." Web: only after a click, HTTPS only. If denied, search + map always still work. Location is a shortcut, never a gate. ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆ 📍 ┆ Use your location? ┆ We use it once to place your ┆ pin faster. You can also ┆ search or move the map. ┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆ ┆ Use my location ┆ ┆ → OS permission prompt └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆ Not now ┆ → stay on map, no prompt └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ 11.2 Pin screen (shared component — shop, buyer, add-address) Behaviour: Fixed centre pin, the map moves (Bolt/Uber pattern). Pin lifts while dragging, drops when the map stops. Start position: accurate GPS → last used location → centre of user's city. Never whole-country view. Map / Satellite toggle (satellite matters — many streets unnamed). GPS accuracy circle ; if accuracy > 100 m show "Location is approximate — move the map to your exact spot". Confirm disabled until zoom ≥ 17 (street level). Hint: "Zoom in to place exactly". Search (Google Places) only moves the map: "Now move the map to the exact entrance". When map stops (debounce ~400 ms): show Google label + call /locations/resolve . If covered=false → disable Confirm, show "We don't deliver here yet". ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ← Shop location Step 3/4 ┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆ ┆ 🔍 Search place or area ┆ ┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆ ┆ [Map|Satellite] ┆ ┆ ┆ ┆ ┆ ┆ ( ◌ ) ← accuracy ┆ ┆ ┆ 📍 fixed centre ┆ ┆ ┆ move the map ┆ ┆ ┆ [◎] ┆ [◎] = use my location ┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆ ⚠ Zoom in to place exactly ┆ (shown until zoom ≥ 17) ┆ 📍 Sinza, Ubungo, Dar es Salaam ← Google label (display only) ┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆ ┆ Confirm location → ┆ ┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ 11.3 Shop flow (mandatory, step in shop creation) ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ← Shop location Step 3/4 ┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆ ┆ [mini map 📍] Change ┆ ┆ ┆ Makurumla, Ubungo, Dar ┆ ┆ ← from /resolve (NBS) └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆ Directions / landmark * ┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆ ┆ Near Shekilango stop, ┆ ┆ ┆ above Vodashop, 1st floor ┆ ┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆ Building / shop no. (optional) ┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆ ┆ Shop 12 ┆ ┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆ Pickup contact phone * ┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆ ┆ +255 7XX XXX XXX ┆ ┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆ Official address (optional) ┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆ ┆ Anwani za Makazi ┆ ┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆ 📷 Add shop front photo (optional) ┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆ ┆ Save & continue → ┆ ┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ If response has FAR_FROM_DEVICE → dialog "Your pin is 3.2 km from where you are. Is this your shop?" [Yes, it's correct] [Adjust pin]. 11.4 Buyer delivery flow (pin only, Bolt style) Checkout — choose where ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ Deliver to ┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆ ┆ ● 🏠 Home (default) ┆ ┆ ┆ Mbezi Juu, Ubungo ┆ ┆ ┆ ○ 💼 Work ┆ ┆ ┆ Kivukoni, Ilala ┆ ┆ ┆ ○ ⭐ Mama's place ┆ ┆ ┆ Tabata, Ilala ┆ ┆ ├ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┤ ┆ ┆ Recent ┆ ┆ ┆ ○ 🕘 Kijitonyama [Save] ┆ ┆ ├ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┤ ┆ ┆ ＋ New location (pin) ┆ ┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆ Manage addresses └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ First-time buyer with nothing saved → goes straight to the pin screen. New location — full map + bottom sheet ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ← Deliver to [Sat] ┆ ┆ FULL MAP ┆ 📍 ┆ [◎] ┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆ ┆ 🔍 Search ┆ ┆ ┆ 🏠 Home Mbezi Juu ┆ ┆ ← tap jumps the pin there ┆ 💼 Work Kivukoni ┆ ┆ ┆ 🕘 Recent Kijitonyama ┆ ┆ ├ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┤ ┆ ┆ 📍 Mikocheni, Kinondoni ┆ ┆ ┆ [ Deliver here → ] ┆ ┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ Quick confirm sheet ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ 📍 Mikocheni, Kinondoni ┆ ┆ Note for rider (optional) ┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆ ┆ Black gate, call on arrival┆ ┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆ Receiver: Me (+255 7XX…) ✎ ← "Someone else" → name + phone ┆ ┆ [ ] Save as 🏠 💼 ✎ ← labels shown only when ticked ┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆ ┆ Continue → ┆ ┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ Profile — manage addresses ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ← My addresses ┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆ ┆ 🏠 Home ✓default ⋮ ┆ ┆ ┆ Mbezi Juu, Ubungo ┆ ┆ ├ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┤ ┆ ┆ 💼 Work ⋮ ┆ ┆ ┆ Kivukoni, Ilala ┆ ┆ ├ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┤ ┆ ┆ ⭐ Mama's place ⋮ ┆ ┆ ┆ Tabata, Ilala ┆ ┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆ ⋮ = Edit pin · Rename · ┆ Set default · Delete ┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆ ┆ ＋ Add address ┆ ┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆ 🕘 Clear recent locations └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ Optional secondary onboarding (buyer) ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆ 📦 ┆ Faster checkout? ┆ Add your home address now ┆ and skip it at checkout. ┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆ ┆ Add address ┆ → pin screen → quick confirm (Save always on) ┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆ Maybe later └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ Area lines shown after saving (lists, checkout) are built from NBS names ( ward, district ) plus the user's label — never from Google text. 12. Flows 12.1 Shop sets location sequenceDiagram actor Owner participant App participant Google as Google Maps/Places (client) participant API as Location module participant DB as PostGIS Owner->>App: Step 3 "Shop location" App->>Owner: Explainer → tap "Use my location" App->>App: OS permission (while in use), one GPS reading Owner->>App: Move map under fixed pin, zoom ≥ 17 App->>Google: label for map centre (display only) App->>API: GET /locations/resolve?lat&lng API->>DB: ST_Contains / nearest ≤ 500 m DB-->>API: ward, district, region API-->>App: covered=true, areaLabel Owner->>App: Confirm → landmark, phone, (building, photo) App->>API: PUT /shops/{id}/location (+deviceLat/Lng) API->>DB: resolve again, upsert shop_locations API-->>App: saved (+ FAR_FROM_DEVICE warning if > 1 km) 12.2 Buyer checkout with a new pin sequenceDiagram actor Buyer participant App participant Orders as Orders/Checkout participant Loc as Location module participant DB as PostGIS Buyer->>App: Checkout → "＋ New location" Buyer->>App: Place pin, note, receiver, [Save?] App->>Loc: GET /locations/resolve (live while moving) Buyer->>App: Continue / Pay App->>Orders: place order { newPin, saveForLater } Orders->>Loc: snapshotFromNewPin(user, req) Loc->>DB: resolve ward alt saveForLater = true Loc->>DB: insert user_addresses (rules §7.2) else Loc->>DB: upsert recent_locations (max 5, 60 days) end Loc-->>Orders: AddressSnapshot (frozen) Orders->>DB: store order + pickup & drop-off snapshots 12.3 Shop publish guard Shop "Publish" → shopModule calls location.hasShopLocation(shopId) ├─ true → publish └─ false → 400 SHOP_LOCATION_REQUIRED → app opens Shop location step 13. Out of scope (do NOT build now) Shipping, providers (Bolt etc.), quotes, tracking, recommendation engine Delivery zones and hubs (future: same pattern — shapes table + ST_Contains ) Mtaa/street level (no public shapes; future table identical to tz_wards if NBS provides them) "Near me" feed (index on shop_locations is prepared; feature later — must use rough area only, not stored) Any backend call to Google; storing Google labels 14. Acceptance tests 14.1 Ward resolution (integration test against loaded data — these were verified against the file) Place lat lng Expected ward District Region Kariakoo market -6.8190 39.2768 Kariakoo Ilala Dar es Salaam Ubungo bus terminal -6.7889 39.2083 Ubungo Ubungo Dar es Salaam JNIA airport -6.8781 39.2026 Kipawa Ilala Dar es Salaam Posta / city centre -6.8160 39.2900 Kivukoni Ilala Dar es Salaam Stone Town -6.1622 39.1887 Shangani Mjini Mjini Magharibi Arusha clock tower -3.3700 36.6940 Sekei Arusha Arusha Mwanza centre -2.5164 32.9006 Nyamagana Nyamagana Mwanza Mbeya town -8.9094 33.4608 Ruanda Mbeya Mbeya Dodoma centre -6.1722 35.7395 Majengo Dodoma Dodoma Indian Ocean off Dar -6.80 39.40 — OUTSIDE_COVERAGE Nairobi -1.2864 36.8172 — OUTSIDE_COVERAGE Also: SELECT count(*) FROM tz_wards = 4344 ; SELECT count(DISTINCT reg_name) = 31 . Use Testcontainers with postgis/postgis image if the project already uses Testcontainers; otherwise follow project test setup. 14.2 Rules Seeder runs twice → still 4344 rows, second run instant. Two app instances start together → 4344 rows, no errors (advisory lock). Missing ward file → app starts, WARN logged, /resolve returns 503. Swapped lat/lng (39.2768, -6.8190) → OUTSIDE_COVERAGE (guards against order bug). 11th saved address → ADDRESS_LIMIT_REACHED . Second HOME → LABEL_ALREADY_USED . Save within 50 m of existing → 409 NEAR_DUPLICATE ; with allowNearDuplicate=true → saved. Delete default → no default remains. First saved address → becomes default. 6th unsaved pin → only 5 recents remain; entries > 60 days not returned. Edit saved address after an order → order snapshot unchanged. Shop without location cannot publish → SHOP_LOCATION_REQUIRED . Shop PUT with device 3 km away → saved + FAR_FROM_DEVICE warning. Seller view of order shows area only unless sellerDelivers=true . TRUNCATE tz_wards + restart → reload + saved addresses re-resolved. 15. Build order Docker: switch DB to postgis/postgis (same PG major), mount /opt/nexgate/geo , add config, .gitignore data/geo/ . WardDataSeeder + WardResolver + GET /locations/resolve + tests §14.1. ← foundation Shop location (entity, PUT/GET, hasShopLocation , publish guard). Buyer addresses + recents (+ rules tests). AddressSnapshot + checkout integration + privacy views. Clients: shared pin-screen component, shop step, checkout picker, manage addresses, optional onboarding.