Engineering

Technical architecture

A pragmatic stack chosen to ship a premium mobile MVP within $20k while remaining production-grade and scalable to 1M+ users.

Mobile framework: React Native (recommended)

Criteria	React Native	Flutter	Winner
Hiring pool	Largest JS/React talent pool	Smaller, Dart-specific	RN
Mapbox SDK	First-class @rnmapbox/maps	flutter_mapbox_gl less mature	RN
3rd-party libs	Vast — Stripe, Sentry, Posthog all native	Growing but gaps remain	RN
Animation polish	Reanimated 3 + Skia, excellent	Flutter native — slightly better OOTB	Flutter
MVP velocity at $20k	Highest with Expo + EAS Build	Comparable	RN
Bundle size	~25MB	~15MB	Flutter
Code reuse w/ future web	Easy via React Native Web	Harder	RN

Decision: React Native (Expo SDK, EAS Build, Reanimated 3, Skia for cosmic effects, @rnmapbox/maps).

Backend: Supabase (recommended)

Criteria	Supabase	Firebase	Node + Postgres	Winner
Auth (Apple/Google/email)	Built-in	Built-in	Build yourself	Tie
Geospatial queries	PostGIS native	GeoFire workaround	PostGIS native	Supabase
Realtime updates	Postgres logical replication	First-class	Build yourself	Firebase
Vendor lock-in	Low — portable Postgres	High	None	Supabase
MVP cost @ 10k MAU	~$25/mo	~$80/mo (Firestore reads)	~$60/mo + ops time	Supabase
Storage	S3-compatible buckets	Firebase Storage	S3/R2	Tie

Decision: Supabase — PostGIS gives us radius search, polygon queries, and clustering for free; portable Postgres avoids lock-in.

Infrastructure overview

┌────────────────────────────────────────────────────────────────┐
│                    React Native (Expo)                         │
│  Screens · Reanimated · Mapbox · Zustand · TanStack Query      │
└────────────────────────┬───────────────────────────────────────┘
                         │ HTTPS / WSS
            ┌────────────┴────────────┐
            │                         │
   ┌────────▼─────────┐    ┌──────────▼───────────┐
   │  Supabase Edge   │    │  Mapbox API          │
   │  Functions       │    │  - Tiles             │
   │  (Deno · TS)     │    │  - Geocoding         │
   │  - createMarker  │    │  - Static maps       │
   │  - feedRank      │    └──────────────────────┘
   │  - aiRecs (Ph 2) │
   └────────┬─────────┘
            │
   ┌────────▼─────────────────────────────────────┐
   │  Supabase Postgres + PostGIS                 │
   │  - users · markers · ratings · journal · …   │
   │  - RLS policies                              │
   │  - pg_cron for nightly score recompute       │
   └────────┬─────────────────────────────────────┘
            │
   ┌────────▼─────────────┐  ┌────────────────────┐
   │ Supabase Storage     │  │ External services  │
   │ - photos/            │  │ - Sentry (errors)  │
   │ - avatars/           │  │ - PostHog (analyt) │
   └──────────────────────┘  │ - Resend (email)   │
                             │ - OneSignal (push) │
                             └────────────────────┘

Geospatial strategy

Storage

PostGIS geography(Point, 4326) on energy_markers.location.
GIST index for O(log n) radius queries.
Coordinates rounded to 5 decimals (~1m) for storage.

Clustering

Server-side: ST_ClusterDBSCAN at zoom ≤ 11.
Client-side: supercluster.js for zoom 12+ for smooth interactions.
Edge function caches cluster results in Postgres-backed KV (5 min TTL).

GPS verification

Edge function recomputes distance between submitted coord and Mapbox-validated location.
Reject if Δ > 100m or accuracy > 50m.
Time-of-day + speed heuristics to flag spoofing.

Privacy

Public read: location fuzzed to nearest 30m grid.
Owner read: exact coords.
User home-location never stored.

Map vendor: Mapbox (recommended)

Feature	Mapbox	Google Maps SDK	Winner
Custom dark cosmic style	Studio editor — full control	Limited theming	Mapbox
Pricing at 50k MAU	~$200/mo	~$700/mo	Mapbox
Offline tile cache	Native support	Premium tier only	Mapbox
RN SDK	@rnmapbox/maps — solid	react-native-maps — solid	Tie
Vector tiles + perf	Excellent	Excellent	Tie

Cross-cutting concerns

Observability

Sentry (mobile + edge), PostHog product analytics, Supabase logs.

CI/CD

GitHub Actions → EAS Build → TestFlight & Play Internal.

Feature flags

PostHog flags; killswitch for AI recs, premium gates.

Postgres trigram on titles + Mapbox geocoding for places.

Push

OneSignal — supports iOS critical + Android channels.

Resend for transactional; weekly digest via cron.