redis-caching

ADR 006: Redis for Caching & Idempotency (Over In‑Memory Only)

Context:
We need a low‑latency cache for seat‑map lookups and a shared store for idempotency keys across pods.

Decision:
Deploy a Redis cluster (with TTL, LRU eviction) for read cache and idempotency, leveraging Redlock for stampede protection.

Consequences:

• Pros:
  • Sub‑millisecond reads/writes, TTL controls staleness.
  • Centralized idempotency store shared by all instances.
• Cons:
  • Single additional datastore to operate and monitor.
  • Potential for cache‑miss thundering without proper mutexing.

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