goplt/docs/content/adr/0022-cache-implementation.md

ADR-0022: Cache Implementation

Status

Accepted

Context

The platform needs caching for:

• Performance optimization (reduce database load)
• Frequently accessed data (user permissions, roles)
• Session data (optional)
• Query results

Options considered:

1. Redis - Industry standard, feature-rich
2. In-memory cache - Simple, no external dependency
3. Memcached - Simple, but less features than Redis
4. No cache - Simplest, but poor performance at scale

Decision

Use Redis as the primary cache with in-memory fallback:

1. Primary: Redis for production
2. Fallback: In-memory cache for development/testing
3. Interface abstraction: Cache interface allows swapping implementations
4. Use cases: Permission lookups, role assignments, query caching

Rationale:

• Industry standard, widely supported
• Rich feature set (TTL, pub/sub, etc.)
• Can be shared across instances (multi-instance deployments)
• Good performance
• Easy to abstract behind interface

Consequences

Positive

• High performance
• Shared across instances
• Rich feature set
• Easy to scale horizontally
• Abstraction allows swapping implementations

Negative

• Additional infrastructure dependency
• Network latency (minimal with proper setup)
• Need to handle Redis failures gracefully

Implementation Notes

• Install: github.com/redis/go-redis/v9
• Create pkg/infra/cache/cache.go interface
• Implement internal/infra/cache/redis_cache.go
• Implement internal/infra/cache/memory_cache.go for fallback
• Use connection pooling
• Handle Redis failures gracefully (fallback or error)
• Configure TTLs appropriately (e.g., 5 minutes for permissions)