What is the difference between write-back and write-through caching?

Question

Accepted Answer

**Write-Back** — write to cache, async to DB. **Write-Through** — write to cache and DB.

**Write-Back (Write-Behind):**
- Write to cache first.
- Async write to DB.
- Fast writes.
- Possible data loss.

```
Write-Back:
App → Cache (fast)
      → DB (async)
(Fast, possible data loss)
```

**Write-Through:**
- Write to cache and DB.
- Synchronous.
- Consistent data.
- Slower writes.

```
Write-Through:
App → Cache → DB (simultaneously)
(Consistent, slower)
```

**Key differences:**
- **Write-Back** — async to DB.
- **Write-Through** — sync to DB.
- **Write-Back** — faster.
- **Write-Through** — consistent.

Systems Analyst: What is the difference between write-back and write-through caching?