I'm interested in what sort of problems you had with Phusion Passenger. What makes you say it is slow and bloated? We've even had users who switched away from Puma and Unicorn for the exact same reasons you mentioned.

But in our experience the app server is rarely the cause of such problems. Most people who complained about bloat in Unicorn/Puma/Passenger eventually discovered that it was a problem at the application level after all.

We'd be happy to help you with your issues if you can tell us more.