Explain Cache-Aside vs Read-Through vs Write-Through vs Write-Back.

Cache-aside, read-through, write-through, and write-back are caching strategies that define how data is read from or written to the cache and database for performance and consistency.

When to Use

• Cache-aside: Great for read-heavy workloads where you load into cache only on demand.
• Read-through: Simplifies client code since the cache auto-fetches from DB on misses.
• Write-through: Ideal when you want strong consistency—writes go to both cache and DB.
• Write-back: Best for write-heavy scenarios, buffering updates in cache first for speed.

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Example

Cache-aside: app checks cache, hits DB on miss. Read-through: app always reads cache; cache fetches DB if needed. Write-through: data written to cache + DB at once. Write-back: data written to cache, DB updated later.

Why Is It Important

Picking the right caching strategy reduces latency, saves DB load, and balances speed with consistency.

Interview Tips

Define each clearly, compare them in terms of reads/writes and consistency, and use a simple analogy to show practical understanding.

Trade-offs

Cache-aside/manual vs read-through/automatic loading. Write-through/strong consistency vs write-back/high speed but risk of data loss.

Pitfalls

Forgetting cache invalidation (stale data) or using write-back for critical data (risk of loss on crash).