Diagnosing slow ActiveRecord queries, N+1 issues, and performance mismatches between SQL and Rails, using real production examples.
The database had indexes. ActiveRecord queries weren't using them. Here's how ActiveRecord query patterns bypass indexes and how to check EXPLAIN output.
WHERE with hash, string, and .or() syntax — all in one guide. Multiple conditions, AND/OR logic, WHERE vs HAVING, and inspecting SQL output. Rails 7/8, 2026.
Ruby 4.0.0 is out. For Rails developers, here's what actually changes: removed APIs, performance gains, and the breaking changes that hit ActiveRecord.
Rails 8.2 for production apps: caching, query performance, concurrency changes, and what actually breaks at scale. No hype, just impact. Updated 2026.