What is the difference between database connection pooling and caching?

Question

Accepted Answer

**Connection Pooling** — reusing database connections. **Caching** — storing query results.

**Connection Pooling:**
- Reuses existing connections.
- Avoids connection overhead.
- Limits concurrent connections.
- Configured in application server.

```
Connection Pooling:
App → [Pool: 10 connections] → DB
  Request 1 → Connection 1
  Request 2 → Connection 2
  Request 3 → Connection 1 (reused)
(Connections recycled)
```

**Caching:**
- Stores query results.
- Avoids repeated queries.
- Various TTL strategies.
- Redis, Memcached.

```
Caching:
App → Cache (Redis) → DB
  Query 1: Cache miss → DB → Store in cache
  Query 2: Cache hit → Return cached
(Results reused)
```

**Key differences:**
- **Pooling** — connection reuse.
- **Caching** — data reuse.
- **Pooling** — reduces overhead.
- **Caching** — reduces queries.

Systems Analyst: What is the difference between database connection pooling and caching?