Strictly typed SQL with Contra CTO, Gajus Kuizinas

In this episode, Gajus Kuizinas, co-founder and CTO of Contra, joins Aaron to talk about building the engineering world you want to live in, from strict runtime-validated SQL with Slonik to creating high-ownership engineering cultures. They dive into developer experience, runtime assertions, SafeQL, and even “Loom-driven development,” a powerful review process that lets teams move fast without breaking things.Follow Gajus:Twitter/X:  https://twitter.com/kuizinasSlonk: https://github.com/gajus/slonikScaling article: https://gajus.medium.com/lessons-learned-scaling-postgresql-database-to-1-2bn-records-month-edc5449b3067Follow Aaron:Twitter/X:  https://twitter.com/aarondfrancis Database School: https://databaseschool.comDatabase School YouTube Channel: https://www.youtube.com/@UCT3XN4RtcFhmrWl8tf_o49g  (Subscribe today)LinkedIn: https://www.linkedin.com/in/aarondfrancisWebsite: https://aaronfrancis.com - find articles, podcasts, courses, and more.Chapters:00:00 – Introduction01:03 – Meet Gajus and Contra01:48 – What Contra does and how it’s different05:34 – Why Slonik exists & early career origins07:47 – The early Node.js era and frustrations with ORMs09:50 – SQL vs abstractions and the case for raw SQL10:35 – Template tags and the breakthrough idea12:03 – Strictness, catching errors early & data shape guarantees13:37 – Runtime type checking, Zod, and performance debates16:02 – SafeQL and real-time schema linting17:01 – Synthesizing Slonik’s philosophy21:29 – Handling drift, static types vs reality22:52 – Defining schemas per-query & why it matters27:59 – Integrating runtime types with large test suites31:00 – Scaling the team and performance tradeoffs33:41 – Runtime validation cost vs developer productivity35:21 – Real drift examples from payments & external APIs38:21 – User roles, data shape differences & edge cases39:51 – Integration test safety & catching issues pre-deploy40:52 – Contra’s engineering culture41:47 – Why traditional PR reviews don’t scale43:22 – Introducing Loom-Driven Development45:12 – How looms transformed the review process52:38 – Using GetDX to measure engineering friction53:07 – How the team uses AI (Claude, etc.)56:26 – Closing thoughts on DX and engineering philosophy58:05 – Contra needs Postgres experts59:00 – Where to find Gajus