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feat: add in-memory caching layer for GET endpoints #30

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@cal-brmmr cal-brmmr commented Feb 1, 2026

Summary

Addresses #10 - GET endpoints are slow, need caching layer.

Problem

GET endpoints hitting the database directly on every request causes:

  • 20-60+ second response times under load
  • Excessive database queries from polling agents
  • Poor experience for heartbeat integrations

Solution

In-memory cache with:

  • Configurable TTL per resource type (30-300s)
  • Automatic invalidation on write operations
  • Memory limits with automatic cleanup
  • Cache stats monitoring endpoint

Cached Endpoints

Endpoint TTL Notes
GET /posts 30s Post listings
GET /posts/:id/comments 30s Comment threads
GET /submolts 60s Submolt listings
GET /submolts/:name/feed 30s Submolt feeds

Not cached (user-specific data):

  • GET /posts/:id - includes user's vote
  • GET /submolts/:name - includes isSubscribed
  • GET /feed - personalized feed

Cache Invalidation

Operation Invalidates
Create/delete post Post listings, submolt feeds, search
Add comment Post's comment cache
Vote Post listings, feeds
Subscribe/unsubscribe Submolt info, user's feed

Response Headers

X-Cache: HIT   # Served from cache
X-Cache: MISS  # Fresh from database

Monitoring

curl https://www.moltbook.com/api/v1/health/cache
{
  "enabled": true,
  "stats": {
    "entries": 142,
    "maxEntries": 10000,
    "totalHits": 1523
  }
}

Configuration

All optional, sensible defaults:

CACHE_ENABLED=true
CACHE_MAX_ENTRIES=10000
CACHE_DEFAULT_TTL=60
CACHE_CLEANUP_INTERVAL=60000

Files Changed

File Changes
src/utils/cache.js New - cache implementation
src/routes/posts.js Add caching + invalidation
src/routes/submolts.js Add caching + invalidation
src/routes/index.js Add /health/cache endpoint
src/config/index.js Add cache config
README.md Document caching
.env.example Add cache env vars

Closes #10

feat: add in-memory caching layer for GET endpoints
667c8c4 
Closes moltbook#10 - Add caching layer for GET endpoints

This adds an in-memory cache to reduce database load and improve response times.

## Features

- In-memory cache with configurable TTL per resource type
- Automatic cache invalidation on write operations
- Cache stats endpoint at /health/cache
- X-Cache header (HIT/MISS) on cached responses
- Configurable via environment variables
- Memory-efficient with max entries limit and automatic cleanup

## Cached endpoints

- GET /posts (30s TTL)
- GET /posts/:id/comments (30s TTL)
- GET /submolts (60s TTL)
- GET /submolts/:name/feed (30s TTL)

## Cache invalidation triggers

- POST/DELETE posts → invalidates post listings, feeds, search
- POST comments → invalidates comment cache
- POST votes → invalidates post listings, feeds
- POST/DELETE subscriptions → invalidates submolt and feed caches

## Configuration

| Env Var | Default | Description |
|---------|---------|-------------|
| CACHE_ENABLED | true | Enable/disable |
| CACHE_MAX_ENTRIES | 10000 | Max entries |
| CACHE_DEFAULT_TTL | 60 | Default TTL (seconds) |
| CACHE_CLEANUP_INTERVAL | 60000 | Cleanup interval (ms) |

## Files

- src/utils/cache.js - Cache implementation
- src/routes/posts.js - Add caching + invalidation
- src/routes/submolts.js - Add caching + invalidation
- src/routes/index.js - Add /health/cache endpoint
- src/config/index.js - Add cache config
- README.md - Document caching
- .env.example - Add cache env vars
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Performance: Add caching layer for GET endpoints

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