deangrant Cache Invalidation Strategies
Use this skill when deciding how cached API responses become fresh.
1. Strategies
| Strategy | Idea |
|---|---|
| TTL / max-age | Time-based expiry |
| ETag / 304 | Revalidate cheaply |
| stale-while-revalidate | Serve stale while refreshing |
| Surrogate-Key / tag purge | Explicit CDN/edge purge by key |
| Hybrid | Short TTL + event-driven purge |
2. Guidance
- Prefer event-driven purge for correctness-critical data; TTL for soft freshness.
- Include auth/tenant in cache keys.
- Avoid thundering herds: SWR, soft locks, or randomized expiry.
3. Quick checklist
- Freshness requirements classified (soft vs hard).
- Key design includes tenant/user where needed.
- Purge path tested for tagged content.
- Stampede mitigations for popular keys.
See reference.md and examples.md.