Just to throw my hat in the ring, Currently CTO /founding engineer of health tech company that runs a Rails backend that serves about 150QPS.

I hear over and over that rails doesn’t “scale”.

Performance wise, we have never had a problem scaling rails itself. The issues were always at the database level. Most slow endpoints (1.5s+) are 10% Ruby, 90% Postgres.

Even if Ruby was magically infinitely fast, these endpoints would go from 1.5s -> 1.35s.

Optimizing data infrastructure gets 10x returns compared to the application code.

Maintenance wise, it’s a bit harder, Rails loves to put everything in the global namespace. This comes down to your team being conscious of properly namespacing different logical parts of your app.