This might be the case "out of the box", but it's very simple to go multithreaded on the Cedar stack and avoid this issue (provided that your app is threadsafe,

This might be the case "out of the box", but it's very simple to go multithreaded on the Cedar stack and avoid this issue (provided that your app is threadsafe, of course). You can do this pretty easily with a Procfile and thin: bundle exec thin -p $PORT -e $RACK_ENV --threaded start And then config.threadsafe! in the app Regarding Rails app threadsafety, there are some gotchas around class-level configuration and certain gems, but by and large these issues are easily manageable if you watch out for them during app development.