Originally published on EugeneTheEngineer.com.
2026 update: This case study started the PostgreSQL series on this blog. Continue with the PostgreSQL Performance Playbook – especially 250ms → 20ms, The Index Lie, and Cross-Examining EXPLAIN.
I believe that virtually every project using Ruby on Rails and Postgres as its main backend tools is in a constant struggle between development speed, code readability/maintainability, and project performance in production. I will share my experience balancing these three pillars in a case where readability and performance suffered initially, but in the end, I managed to achieve what several talented engineers had unsuccessfully attempted before me.
The whole story will take several parts. This is the first one, where I'll talk about what PMDSC is for optimizing SQL queries, share useful tools for measuring query performance in Postgres, and remind you of one useful old cheat sheet that is still relevant.
Now, after some time has passed, in hindsight, I realize that I didn't expect everything to work out in this case. Therefore, this post will be more useful for bold and less experienced developers than for super-seniors who have seen Rails with raw SQL.
