Design Distributed Cache

What is a Cache?

A cache is a high-speed data storage layer that stores a subset of data so that future requests for that data are served faster.

Cache Eviction Policies

• •LRU (Least Recently Used): Evict the item not used for the longest time
• •LFU (Least Frequently Used): Evict the item with fewest accesses
• •FIFO: First in, first out
• •Random: Evict random items

Cache Write Strategies

• •Write-through: Write to cache AND DB simultaneously. Consistent but slow writes.
• •Write-back: Write to cache only; DB updated later. Fast writes but risk of data loss.
• •Write-around: Write directly to DB, bypass cache. Good for data written once.

Cache Read Strategies

• •Cache-aside (Lazy Loading): App checks cache → miss → reads DB → updates cache
• •Read-through: Cache handles DB reads automatically on miss