Social API — Rust Microservice

Production-ready microservice for social interactions (Likes) across content types. Built with Rust, Axum, PostgreSQL, and Redis.

Architecture

• API Layer: Axum web framework with REST endpoints
• Database: PostgreSQL 15+ with read replica support
• Cache: Redis for like counts (hot path), content validation, rate limiting
• Content Validation: Pluggable interface — add new content types via config only

Token-based Pagination

User likes use token-based pagination (not offset) because:

• Consistency: Offset pagination can skip/duplicate items when data changes during pagination
• Performance: WHERE (created_at, id) < (ts, id) uses the index efficiently; offset requires scanning N rows
• Scale: Tokens don't degrade with large offsets

Caching Strategy

• Like counts: Redis, TTL 300s. Invalidated on write. Fallback to DB when Redis unavailable.
• Content validation: Redis, TTL 3600s. Reduces external API calls.
• Cache stampede: Single-flight pattern (simplified in initial implementation).

Quick Start

docker compose up --build

Service: http://localhost:8080

Smoke Test

# Health
curl -s http://localhost:8080/health/ready | jq .

# Like count (public)
curl -s http://localhost:8080/v1/likes/post/731b0395-4888-4822-b516-05b4b7bf2089/count | jq .

# Like (auth)
curl -X POST http://localhost:8080/v1/likes \
  -H "Authorization: Bearer tok_user_1" \
  -H "Content-Type: application/json" \
  -d '{"content_type":"post","content_id":"731b0395-4888-4822-b516-05b4b7bf2089"}' | jq .

API Endpoints

Method	Path	Auth	Description
POST	/v1/likes	Bearer	Like content
DELETE	/v1/likes/{type}/{id}	Bearer	Unlike
GET	/v1/likes/{type}/{id}/count	—	Like count (cached)
GET	/v1/likes/{type}/{id}/status	Bearer	User like status
GET	/v1/likes/user	Bearer	User's likes (page_token)
POST	/v1/likes/batch/counts	—	Batch like counts
POST	/v1/likes/batch/statuses	Bearer	Batch like statuses
GET	/v1/likes/top	—	Top liked (leaderboard)
GET	/v1/likes/stream	—	SSE like events
GET	/health/live	—	Liveness
GET	/health/ready	—	Readiness
GET	/metrics	—	Prometheus metrics

Configuration

Variable	Required	Default
DATABASE_URL	Yes	—
READ_DATABASE_URL	No	DATABASE_URL
REDIS_URL	Yes	—
HTTP_PORT	No	8080
CONTENT_API_POST_URL	No	http://mock-post-api:8081
CONTENT_API_BONUS_HUNTER_URL	No	http://mock-bonus-hunter-api:8082
CONTENT_API_TOP_PICKS_URL	No	http://mock-top-picks-api:8083
PROFILE_API_URL	No	http://mock-profile-api:8084

Mock Services

• Content API: GET /v1/{content_type}/{content_id} — returns 200 with items for valid UUIDs
• Profile API: GET /v1/auth/validate with Bearer token — returns user_id for tok_user_1..5

License

MIT