HighFile-scopeRuby Plug & play

Optimize queries with joins and includes

Use joins for filtering on associations and includes/preload for eager-loading to avoid N+1.

Why this matters

Reduces query count and latency.

Side-by-side examples engineers can pattern-match during review.

Avoid

posts.each { |p| puts p.user.name }

Prefer

posts = Post.includes(:user)
posts.each { |p| puts p.user.name }

Bad

User.where(posts: { id: ids }) without join

Good

User.joins(:posts).where(posts: { id: ids })

From the same buckets as this rule.

Critical
Block risky database migrations (locking ops, downtime risk)
Review SQL/database migrations for operations that can lock large tables or cause downtime. Examples: creating indexes without CONCURRENTLY (Postgres), ALTER COLUMN TYPE on big tables, adding NOT NULL without backfill, long-running updates without batching. Require an online migration strategy (CONCURRENTLY, backfill in batches, dual-write/expand-contract) and a rollback plan.
migrations-backward-compatdatabase-query-performance
High
Add database indexes for query optimization
Index frequently filtered or joined columns and verify with query plans.
database-query-performanceperformance-efficiency
High
Add database indexes for query performance
Index columns used in WHERE/JOIN/ORDER and enforce uniqueness where applicable.
database-query-performance