caching

Cache-aside without an invalidation story ships stale pricing to 2% of users—the hardest 2% to debug. This guide layers CloudFront, ElastiCache, and DAX with TTL, event-driven purge, and when write-through beats cache-aside.

RDS performance: gp3 IOPS, Performance Insights / Database Insights, Proxy, replicas, ElastiCache. July 2026 tuning checklist.

Valkey on ElastiCache: about 20% node / 33% serverless cheaper than Redis OSS engines. July 2026 — sessions, rate limits, locks, migration checklist.

Redis is fast — until your application retries on every cache miss and the Redis bill starts looking like the database bill. ElastiCache patterns, data structures, cluster modes, eviction policies, and the production patterns that actually reduce database load.