activerecord

Scopes encapsulate reusable query logic directly in the model, improving code readability and reducing duplication across controllers and services. I use scopes for common filters like active, published, or recent rather than writing raw where clauses

N+1 queries are the silent performance killer in Rails apps—they're easy to introduce during rapid development and expensive to diagnose in production. The Bullet gem monitors queries during development and test runs, raising alerts when it detects mi

ActiveRecord provides powerful query interface, but naive usage causes N+1 queries. includes eager loads associations in 2-3 queries. joins performs SQL JOINs for filtering. preload always uses separate queries; eager_load forces LEFT OUTER JOIN. I us

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.

Normalize before validation to avoid “same email, different casing/whitespace” bugs. Keep normalization deterministic and small; put it in the model so imports, consoles, and controllers all behave the same.

When rendering JSON, the serializer layer can silently trigger extra queries. Force “preload then serialize” so your JSON rendering path is deterministic. This pattern scales well in Rails APIs.

Sometimes raw SQL is the cleanest approach—just keep it safe. Use exec_query with bind params instead of interpolating values. You get both safety and correctness with types.

Tagging systems can be expensive. For quick “top tags” features, compute from the join table with group and count. Avoid loading full taggable records.

Hard deletes make data recovery impossible and complicate audit trails. Soft deletes mark records as deleted without removing them from the database, preserving history and enabling undo functionality. The paranoia gem adds a deleted_at timestamp colu

Authorization filters often become string-SQL soup. Use Arel to build composable scopes that are still readable and safe. This snippet shows a “visible_to(member)” scope with a join and a condition that can evolve without turning into interpolated SQL

Inventory systems are concurrency systems. Lock the row, verify available quantity, then write the reservation in the same transaction. It’s the simplest correct starting point.

Eager loading associations with includes, preload, or eager_load is essential for avoiding N+1 queries that kill performance. When rendering a list of posts with their authors, Post.includes(:author) loads all authors in a second query rather than fir