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tasks/web-production/07-caching-strategy.md

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+# 07. Caching Strategy (Redis + HTTP Cache)
+
+meta:
+  id: web-production-07
+  feature: web-production
+  priority: P2
+  depends_on: []
+  tags: [performance, caching, production]
+
+objective:
+- Implement multi-layer caching to reduce database load and improve response times
+
+deliverables:
+- Redis caching layer for API responses
+- HTTP cache headers for client-side caching
+- Cache invalidation strategy
+- Stale-while-revalidate pattern
+
+steps:
+1. Implement Redis caching for API responses:
+   - Create web/src/server/lib/cache.ts with Redis-backed cache
+   - Cache user profile: key `user:{id}`, TTL 5 minutes
+   - Cache subscription: key `sub:{userId}`, TTL 1 minute
+   - Cache dashboard summary: key `dash:{userId}`, TTL 30 seconds
+   - Cache blog posts: key `blog:{slug}`, TTL 1 hour
+2. Add cache decorators/procedures:
+   - Create cachedProcedure wrapper for tRPC
+   - Support cache tags for invalidation
+3. Implement HTTP caching headers:
+   - Static assets: Cache-Control: public, max-age=31536000, immutable
+   - API responses: Cache-Control: private, max-age=30
+   - HTML pages: Cache-Control: no-cache (SSR)
+4. Add cache invalidation:
+   - Invalidate user cache on profile update
+   - Invalidate subscription cache on billing event
+   - Invalidate blog cache on publish/edit
+5. Implement stale-while-revalidate for dashboard data
+6. Add cache hit/miss metrics
+
+tests:
+- Unit: Test cache set/get/delete operations
+- Integration: Test cache invalidation on mutations
+- Performance: Compare cached vs uncached response times
+
+acceptance_criteria:
+- Redis cache layer active on all read-heavy endpoints
+- Cache hit rate >80% for user profile and subscription endpoints
+- Cache invalidation working on all mutations
+- HTTP cache headers correct per endpoint type
+- Stale-while-revalidate pattern on dashboard widgets
+- Cache metrics visible in monitoring dashboard
+
+validation:
+- Load test: cached endpoint p95 < 20ms
+- Verify Redis keys created for cached data
+- Update profile → cache invalidated, next request hits DB
+
+notes:
+- Redis already used for BullMQ jobs — share connection or use separate DB index
+- Be careful caching authenticated data — always include userId in key
+- Consider using Vercel KV or Upstash Redis for serverless