What is the difference between cache-aside and write-through?

Question

Accepted Answer

**Cache-Aside** — app manages cache. **Write-Through** — cache writes to DB.

**Cache-Aside (Lazy Loading):**
- App checks cache first.
- Cache miss → load from DB.
- App manages cache.
- Most common.

```
Cache-Aside:
App → Cache: Get key
  Hit → Return
  Miss → DB → Cache → Return
(App manages)
```

**Write-Through:**
- Write to cache and DB simultaneously.
- Cache ensures DB write.
- Consistent data.
- Write latency.

```
Write-Through:
App → Cache → DB (simultaneously)
  Cache ensures DB write
  (Consistent)
```

**Key differences:**
- **Cache-Aside** — app manages.
- **Write-Through** — cache manages.
- **Cache-Aside** — lazy loading.
- **Write-Through** — immediate.

Systems Analyst: What is the difference between cache-aside and write-through?