caching

ETags enable efficient caching by allowing clients to make conditional requests that return 304 Not Modified when content hasn't changed. Rails automatically generates ETags based on response content, and fresh_when or stale? methods handle the condit

Serializing complex ActiveRecord objects to JSON can consume significant CPU time, especially when rendering collections with nested associations. Fragment caching stores rendered JSON fragments in Redis keyed by a cache key that includes the record's

When a child record changes, you often want the parent cache key to change too. touch: true is a clean primitive for that. It keeps fragment caching sane without complex dependency graphs.

If you have a “top list” that’s expensive to compute, a materialized view is a clean approach. Refresh concurrently on a schedule to keep reads fast without blocking.

A robust feature flag read path should be fast, but also resilient to cache outages. Cache the computed result briefly and fall back to DB if needed; keep the interface dead simple.

Query plan caching improves performance by reusing execution plans. I use prepared statements to parse once, execute many times. PostgreSQL caches plans after 5 executions. Plan invalidation occurs when statistics change. Generic plans vs custom plans

Hotwire doesn’t replace caching—it makes it more valuable because you’re sending HTML frequently. I use fragment caching inside list partials and keep cache keys stable with cache blocks. The pattern is: cache each row by record, and cache the list wr

When caching lists, include inputs that change the list (filters, page, member permissions). A deterministic cache key function prevents subtle “wrong user saw wrong list” bugs.

Kredis provides typed Redis structures as Active Model attributes, simplifying common patterns like counters, flags, and lists. Instead of raw Redis commands, I define kredis accessors on models that handle serialization automatically. Counters track

Loading images from URLs requires caching to avoid redundant network calls and improve performance. I create an image cache using NSCache which automatically evicts objects under memory pressure. The cache stores UIImage or Data keyed by URL. For asyn

When you need to invalidate caches by changing timestamps, use touch_all to avoid per-record callbacks. It’s fast, explicit, and doesn’t run unintended side effects.

Most ‘caching’ bugs are really invalidation bugs, so I stick to a simple cache-aside pattern with conservative TTLs and treat cache misses as normal. The big failure mode to avoid is a stampede: if many requests miss at once, you can crush your DB. Fo