Topics / Caching

Caching

Latency wins, stampede control, and invalidation that does not lie.

Common tags: redis, ttl, cache-aside

• CachingSep 2026

  Distributed Caching Consistency — Local vs Shared Cache & Near-Cache

  Cluster · Redis cache

  A near-cache (L1 in each pod) on top of a shared L2 (Redis) removes the network hop for hot keys, but every write must now reach every pod. Invalidate L2, fan out a versioned message to every L1, keep L1 TTL short, and flush L1 when a subscriber reconnects.

  • near-cache
  • distributed-cache
  • consistency
  • local-cache
  • invalidation-bus
  • interview
  Open study →
• CachingSep 2026

  Cache Invalidation — TTL vs Event-Driven vs Versioned Keys

  Cluster · Redis cache

  Invalidation is how you stop serving lies. TTL is the safety net, event-driven DEL tracks writes, and versions stop a slow reader from writing an old snapshot back after your DEL. Combine them and design for the invalidation path failing.

  • cache-invalidation
  • ttl
  • event-driven
  • versioned-keys
  • cdc
  • consistency
  • interview
  Open study →
• CachingSep 2026

  Write-Through vs Write-Behind Caching

  Cluster · Redis cache

  Cache-aside invalidates after DB commit. Write-through warms cache on the write path. Write-behind acks from cache/queue and flushes later — faster writes, durability risk.

  • caching-data-stores
  • redis
  Open study →
• CachingSep 2026

  Single-Flight Locking for Cache Fills

  Cluster · Redis cache

  Coalesce concurrent misses with SET NX PX. Lock TTL vs load p99. Token + Lua unlock. Waiters poll the data key. Combine with in-process singleflight.

  • caching-data-stores
  • redis
  Open study →
• CachingSep 2026

  Redis Eviction Policies & Memory Management

  Cluster · Redis cache

  maxmemory plus a policy. Caches usually allkeys-lru or allkeys-lfu. volatile-* protects keys without TTL. noeviction makes writes fail. Pick string/hash/list/set/zset/stream from the access pattern; RDB vs AOF vs none from durability. Eviction is not capacity planning.

  • caching-data-stores
  • redis
  Open study →
• CachingSep 2026

  Negative Caching

  Cluster · Redis cache

  Cache the fact that a key does not exist with a distinct sentinel and a short TTL. Invalidate on create. Miss storms on absent keys are as dangerous as hot hits.

  • caching-data-stores
  • redis
  Open study →
• CachingSep 2026

  Cache TTL Design & Jitter

  Cluster · Redis cache

  TTL is a staleness bound. Identical TTLs create expiry cliffs. Add jitter; use soft TTL / XFetch on hot keys; size TTL from business tolerance, not habit.

  • caching-data-stores
  • redis
  • ttl
  Open study →
• CachingSep 2026

  Redis Cache-Aside, Invalidation & Stampede Prevention

  Cluster · Redis cache

  Cache-aside + delete-on-write; TTL jitter; single-flight SET NX PX + Lua unlock; XFetch; negative caching.

  • caching-data-stores
  • redis
  Open study →