Feature Decomposition: Offline Support

Total Stories: 9 stories
Estimated Timeline: ~18 days (assuming 1 team)
Dependencies: Stories 1-2 must complete before Stories 3-8

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🔍 Story 1: Offline Capabilities Investigation [Foundation]

Estimated Size: 2 days
Priority: MUST HAVE (blocks technical decisions)

As a technical lead,
I want to understand current data loss scenarios and offline storage options,
So that we can choose the right offline strategy for mobile and web.

Acceptance Criteria (starters):

• Document all current data loss scenarios reported by users
• Audit mobile app for existing local storage (Core Data, SQLite, etc.)
• Audit web app for existing storage (LocalStorage, IndexedDB, etc.)
• Evaluate sync conflict resolution strategies (last-write-wins, operational transform, CRDT)
• Measure typical data sizes per user session
• Recommend storage approach per platform (mobile vs web)
• Define sync architecture (polling vs WebSocket vs background sync)
• Document security considerations (encryption at rest)

Technical Notes:

• iOS: Consider Core Data + CloudKit or custom SQLite
• Web: IndexedDB preferred over LocalStorage for large data
• Need to understand network reliability patterns from analytics
• Consider offline-first frameworks (Realm, PouchDB, WatermelonDB)

INVEST Check:

• Independent: Can be completed without implementation
• Negotiable: Investigation scope is flexible
• Valuable: Prevents costly rework by making informed decisions
• Estimable: Timeboxed to 2 days
• Small: 2-day spike
• Testable: Delivers decision document with recommendations

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Story 2: Data Sync Infrastructure [Foundation]

Estimated Size: 3 days
Priority: MUST HAVE (blocks other stories)
Dependency: Requires Story 1 (investigation)

As a backend developer,
I want a sync API that handles offline data uploads and conflict resolution,
So that mobile and web clients can reliably sync when reconnected.

Acceptance Criteria (starters):

• Sync endpoint accepts batches of offline actions with timestamps
• Server assigns definitive timestamps to resolve clock skew
• Conflict resolution strategy implemented (based on Story 1 decision)
• Idempotency keys prevent duplicate operations
• Returns sync status per item (accepted, rejected, conflicted)
• API versioning supports client upgrades
• Rate limiting prevents sync abuse
• [Add more based on chosen sync strategy]

Technical Notes:

• Consider event sourcing pattern for audit trail
• Need database transactions for consistency
• Queue system for async processing if large batches
• Metrics for sync success/failure rates

INVEST Check: All criteria met

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Story 3: Mobile Local Storage Layer [Foundation - Mobile]

Estimated Size: 3 days
Priority: MUST HAVE (mobile platform)
Dependency: Requires Story 1 (investigation)

As a mobile developer,
I want a local database to persist user data offline,
So that the app remains functional without connectivity.

Acceptance Criteria (starters):

• Local database implemented (Core Data / SQLite / Realm based on Story 1)
• Schema mirrors backend data models for key entities
• CRUD operations work offline with local storage
• Data encrypted at rest (using device keychain)
• Migration strategy for schema updates
• Query performance acceptable for typical datasets (<100ms)
• [Add more based on storage technology choice]

Technical Notes:

• iOS: Core Data with CloudKit or SQLite.swift
• Consider write-through vs write-back caching
• Need garbage collection for old offline data
• Test with airplane mode enabled

INVEST Check: All criteria met

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Story 4: Web Local Storage Layer [Foundation - Web]

Estimated Size: 2 days
Priority: MUST HAVE (web platform)
Dependency: Requires Story 1 (investigation)

As a web developer,
I want to persist user data locally in the browser,
So that web users don’t lose work when disconnected.

Acceptance Criteria (starters):

• IndexedDB wrapper implemented with promise-based API
• Stores key user actions (form submissions, edits, uploads)
• Schema versioning for database migrations
• Storage quota management (warn at 80% capacity)
• CRUD operations work offline with IndexedDB
• Fallback to in-memory storage if IndexedDB unavailable (privacy mode)
• [Add more based on data volume]

Technical Notes:

• Consider Dexie.js or localForage for IndexedDB wrapper
• Service Worker registration prerequisite
• Test in incognito/private browsing mode
• Handle storage quota exceeded errors

INVEST Check: All criteria met

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Story 5: Mobile Offline Queue [Core - Mobile]

Estimated Size: 3 days
Priority: MUST HAVE (mobile platform)
Dependencies: Stories 2 + 3

As a mobile user,
I want my actions to be saved locally when offline,
So that nothing is lost when my connection drops.

Acceptance Criteria (starters):

• User actions queued in local database when offline
• Queue items include action type, payload, timestamp, retry count
• Visual indicator shows pending sync items count
• Queue persists across app restarts
• Queue processes automatically when online
• Failed sync items retry with exponential backoff
• User can manually trigger sync from settings
• [Add more based on action types]

Technical Notes:

• Reachability observer detects connectivity changes
• Background sync when app returns to foreground
• Consider operation priority (user vs system actions)
• Handle app termination during sync

INVEST Check: All criteria met

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Story 6: Web Offline Queue with Service Worker [Core - Web]

Estimated Size: 3 days
Priority: MUST HAVE (web platform)
Dependencies: Stories 2 + 4

As a web user,
I want my form submissions and edits saved when offline,
So that I can continue working without connectivity.

Acceptance Criteria (starters):

• Service Worker intercepts API requests when offline
• Failed requests queued in IndexedDB
• Queue includes request method, URL, body, headers, timestamp
• Background sync API replays queue when reconnected
• Visual badge shows pending sync count
• Sync notification shows success/failure
• User can view pending changes in UI
• [Add more based on request types]

Technical Notes:

• Service Worker registration and activation lifecycle
• Background Sync API (fallback to polling if unavailable)
• Consider request deduplication
• Handle CORS and auth tokens in replayed requests

INVEST Check: All criteria met

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Story 7: Conflict Resolution UI [Core]

Estimated Size: 2 days
Priority: MUST HAVE (both platforms)
Dependencies: Stories 5 + 6

As a user,
I want to see when my offline changes conflict with server data,
So that I can decide which version to keep.

Acceptance Criteria (starters):

• Modal shows conflicting versions side-by-side
• User can choose “Keep mine”, “Use server”, or “Merge”
• Merge option available for non-destructive conflicts
• Preview shows result before confirming
• Conflict automatically resolved if no overlap (auto-merge)
• User notified of resolved conflicts in activity log
• [Add more based on conflict types]

Technical Notes:

• Diff algorithm to highlight changes
• Consider field-level vs document-level conflicts
• Accessibility: keyboard navigation, screen reader support
• Conflicts stored until user resolves (no silent data loss)

INVEST Check: All criteria met

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Story 8: Offline Indicator & Status [Core]

Estimated Size: 1 day
Priority: MUST HAVE (both platforms)
Dependencies: Stories 5 + 6

As a user,
I want clear indicators of offline mode and sync status,
So that I understand when my data is being saved locally vs synced.

Acceptance Criteria (starters):

• Offline mode banner appears at top when disconnected
• Sync status icon shows “synced”, “syncing”, “offline”, “error” states
• Toast notification when transitioning online/offline
• Pending changes count visible in status bar
• Last successful sync timestamp shown
• Tapping status opens sync detail view

Technical Notes:

• Use platform-native connectivity APIs
• Debounce rapid connection state changes
• Persistent notification vs transient toast
• Icon design for accessibility (colorblind-friendly)

INVEST Check: All criteria met

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Story 9: Offline Data Pruning [Enhancement]

Estimated Size: 2 days
Priority: SHOULD HAVE (storage management)
Dependencies: Stories 3 + 4

As a user with limited device storage,
I want old offline data automatically cleaned up,
So that the app doesn’t consume excessive storage.

Acceptance Criteria (starters):

• Data older than 30 days automatically pruned
• Synced items deleted from local storage after confirmation
• User can manually clear offline cache from settings
• Storage usage shown in settings (MB used)
• Warning shown if storage exceeds threshold (100MB)
• [Add more based on data retention policy]

Technical Notes:

• Background job for pruning (iOS: BGTaskScheduler, Web: Service Worker)
• Keep unsynced data indefinitely (warn user)
• Test with low storage scenarios
• Respect user privacy (clear on app uninstall)

INVEST Check: All criteria met

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Implementation Strategy

Phase 1: Investigation & Foundation (Days 1-8)

• Story 1 (investigation) - 2 days [BLOCKING]
• After Story 1 completes:
  • Story 2 (sync API) - 3 days
  • Story 3 (mobile storage) + Story 4 (web storage) in parallel - 3 days (2 developers)
• Enables: Core infrastructure for offline support

Phase 2: Offline Queues (Days 9-14)

• Story 5 (mobile queue) + Story 6 (web queue) in parallel - 3 days each (2 developers)
• Story 7 (conflict UI) - 2 days
• Enables: MVP offline functionality, shippable

Phase 3: Polish (Days 15-17)

• Story 8 (indicators) - 1 day
• Story 9 (pruning) - 2 days (can run parallel with Story 8)
• Enables: Production-ready offline experience

MVP Definition: Stories 1-7 = Full offline support with conflict resolution (14 days)
Full Feature: All 9 stories (17 days)

Parallelization Opportunities:

• Phase 1: Stories 3 + 4 in parallel → 3 days instead of 5
• Phase 2: Stories 5 + 6 in parallel → 3 days instead of 6
• Phase 3: Stories 8 + 9 in parallel → 2 days instead of 3
• Best case with 2 developers (1 mobile, 1 web): 14 days total

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Risk Mitigation

Technical Risks:

• Storage quota on web → Implement quota warnings, graceful degradation
• Sync conflicts complex → Start with last-write-wins, iterate based on user feedback
• Background sync unreliable → Fallback to foreground sync with manual trigger
• Large data volumes → Implement pagination, partial sync, compression
• Clock skew on devices → Use server timestamps as source of truth

Scope Risks:

• Story 1 reveals complexity → May need to split Story 2 into smaller pieces
• Conflict resolution UX complex → Consider deferring advanced merge features
• Platform differences → May need separate stories for iOS/Android if very different
• Third-party dependencies → Have backup plan if chosen library insufficient

User Experience Risks:

• Users don’t understand offline mode → Comprehensive onboarding, tooltips
• False positives on connectivity → Debounce and validate connectivity checks
• Data loss anxiety → Clear status indicators, confirmation messages

Recommendation: Build Phase 1 + 2 first (14 days), beta test with power users, validate sync reliability and conflict resolution UX before rolling out Phase 3.

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Definition of Done

Each story is complete when:

• Code reviewed and merged
• Unit tests written and passing (>80% coverage for sync logic)
• Integration tests cover offline → online transitions
• Manual QA completed on both platforms (airplane mode testing)
• Performance benchmarks met (sync time <5s for typical session)
• Documentation updated (offline behavior in user guide)
• Security review passed (Stories 2-4)
• Analytics instrumented (sync success rate, conflict frequency)

Platform-Specific DoD:

• Mobile: Tested on iOS 15+, low storage scenarios
• Web: Tested on Chrome/Safari/Firefox, private browsing mode, service worker activation