[jakuboboza]

The scaling factor for each app is really the way it interact with slowest part of the API. If it is Database than no matter how optimal your Rust code is, you might fare in the end not that much better than Rails just because you hinged everything on eg. Postgres.

[throwaway189262]

Db is slow anyways is the default excuse when using slow web backends.

The one I'm currently working on is blazing fast and were truly hitting postgres limits... At nearly 50k requests a second.

The DB is rarely a bottleneck if you have sane structure and indexes. Ironically the slowest frameworks also tend to generate terrible queries (ActiveRecord, SQLAlchemy), so you end up with a slow database and web framework

[dimgl]

I agree with you. I don't think anyone can convince me to use these bloated frameworks on any project ever again in my life.

[spockz]

The assumption here is that you will spend more CPU cycles in your rails app to hit the ceiling of the DB than you will with a performing rust app. So even though you will have the same upper ceiling of scale, reaching it will require less compute and therefore money in your api layer. Whether the difference is significant enough to balance developer FTE depends on the org.