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Cache invalidation strategies, Cache-Aside, Write-Through, Write-Behind, and eviction algorithms.
Cache-Aside (Lazy Loading), Write-Through, Write-Around, and Write-Back (Write-Behind).
Cache-Aside is the most popular strategy. The application queries the cache first; on a miss, it reads from the database and populates the cache.
LRU (Least Recently Used), LFU (Least Frequently Used), FIFO, and TTL expiration.
LRU drops keys that haven't been accessed recently, making it ideal for temporal locality workloads like news feeds or e-commerce products.
Mitigate mass cache miss spikes using probabilistic early expiration (XFetch) or distributed locks.
When a popular key expires, thousands of concurrent requests hit the database simultaneously. Locking ensures only one worker rebuilds the cache while others wait.
Top FAANG and tier-1 system design interview questions.
How do you solve the Cache Penetration problem?
Cache Penetration occurs when queries hit non-existent keys repeatedly. Solution: Use Bloom Filters at the edge to reject invalid keys, or cache null objects with a short TTL.