I'm digging https://github.com/RobertoPrevato/BlackSheep myself, since I prefer the terseness of Bottle and stacking decorators to add functionality to handlers.

Any of the above (or Sanic) can do ~3K RPS on a single core on a Raspberry Pi (which is where I test things for portability, optimisation and a little fun), and the RAM overhead is generally not that bad small (just did a little "hello world" uvicorn/blacksheep app and I see 22MB resident/10MB shared per worker, and one of my Clojure servers taking up over four times that...)