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- 2 Strategies
- Lazy loading
- When something is requested from cache and cache misses, cache request it from origin
- This is the strategy used by CDNs
- Write-through
- When origin is updated, update cache at the same time
- Compare 🎓
- Lazy loading
- Good
- Low storage needs = only cache requested data
- Fault-tolerant = replaced nodes only increases latency but can work normally
- Bad
- Cache miss = latency
- Stale data = no way to update cache when origin data is updated
- Use TTL or use write-through
- Write-through
- Good
- Up-to-date = no stale data
- No cache miss penalty
- Bad
- Write penalty = every writes incurs writing to both cache and database
- Faults result in missing data = when node is replaced there will be a time window of data not written to cache thus missing
- Wasted storage = most data are not accessed but will account into cache storage
- Strategies not exclusive, and be combined and should
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