rails-performancelisted

# Rails Performance Patterns ## 1. Fragment Caching in Views Cache expensive partials with `<% cache record do %>`. The key derives from `cache_key_with_version`, so the fragment invalidates when the record's `updated_at` changes. Nest cache blocks for granular invalidation. ```erb <% cache card do %> <div class="card-perma__actions"> <%= render "cards/container/gild", card: card %> <%= render "cards/container/image", card: card %> </div> <%= card_article_tag card, class: "card" do %> <%= render "cards/display/perma/board", card: card %> <%= render "cards/display/perma/tags", card: card %> <% end %> <% end %> ``` --- ## 2. Collection Caching `cached: true` on collection renders caches each item individually and fetches all of them in one `read_multi` call. Combine with a `preloaded` scope (Pattern 7) to avoid N+1 during rendering. ```erb <%= render partial: "cards/comments/comment", collection: card.comments.preloaded.chronologically, cached: true %> ``` --- ## 3. JSON Caching Use `json.cache!` in Jbuilder templates: ```ruby json.cache! @event do json.id @event.id json.action @event.action json.eventable do json.partial! @event.eventable end end ``` --- ## 4. Don't Over-Cache: The "Fast N+1" Anti-Pattern Granular `Rails.cache.fetch` calls scattered through models and helpers turn a list page into dozens or hundreds of cache round-trips — an N+1 made of cache reads instead of queries. Each read is a networ