Pulse (Mobile Habit + Mood Tracker)

Offline-first mobile app with SQLite outbox sync, OAuth, push reminders, deep links, and share cards

Role

Solo

Focus

Offline-first sync, Outbox pattern, OAuth + account linking

Testing

Detox E2E (iOS), Sync idempotency tests, Deep link validation

Key Patterns

Mobile, Expo, Offline-first, SQLite

MobileExpoOffline-firstSQLiteSyncOAuthPushDetox

What it does

Tracks daily habits and mood check-ins with streaks and weekly insights
Works offline: updates local DB instantly and syncs when online
Supports onboarding, reminders (push), and deep links into specific habits/dates
Generates a shareable streak card image using native share sheet
Includes account linking for real-world auth UX

Architecture

┌────────────────────────┐      ┌────────────────────────┐
│  Expo Mobile App       │─────►│  Fastify API           │
│  (Today/Habits)        │      │  JWT + OAuth exchange  │
└───────────┬────────────┘      └───────────┬────────────┘
            │                               │
            │ SQLite (local)                │ Postgres
            ▼                               ▼
┌───────────────────────┐      ┌──────────────────────────┐
│  SQLite + Drizzle     │      │  Postgres                │
│  habits/mood/outbox   │      │  users/habits/checkins   │
└───────────┬───────────┘      └────────────┬─────────────┘
            │ outbox sync                   │
            ▼                               ▼
┌───────────────────────┐      ┌──────────────────────────┐
│  Sync Engine          │      │  Expo Push Service       │
│  (idempotent ops)     │      │  tokens + reminders      │
└───────────────────────┘      └──────────────────────────┘

Reliability & Guardrails

Local-first writes ensure UX is responsive and resilient to network outages
Outbox + idempotent op IDs prevent double-apply and enable safe retries
Permissions requested only when user opts in (push reminders onboarding step)
Deep links are validated defensively (invalid params fall back to safe routes)
Detox smoke test keeps core flow from regressing (first-run → today interaction)

How to demo in 2 minutes

Start backend DB: docker compose up -d
Run backend migrate/seed; start backend on :4000
Start mobile: cd apps/mobile && npm start
Sign in (demo user) → complete onboarding → toggle habits + set mood
Go offline and toggle → reconnect → verify sync
Open Insights → share a streak card → open deep link from share text

Links

GitHub