[rafekett]

> JSON rendering performance is a major concern for most of my Rails apps

I've always wondered why this is the case. Faster JSON libraries don't seem to help. Similar frameworks don't have this problem. It just seems the Rails serialization code is slow in and of itself, it's not what it calls out to. Maybe there's a contention issue somewhere?

[steveklabnik]

There have been some historical issues that should have been sorted out in more recent releases. The TL;DR is that Rails wouldn't actually use your faster gems, even if you thought it was. See https://github.com/rails/rails/pull/12183 for the work that was done to improve this. There was another issue too that detailed the specific problem, but I can't find it right now.