Replace Express with uWebSockets

[ansarizafar]

Consider replacing expressjs with uWebScket performance gain is huge https://github.com/uWebSockets/uWebSockets/wiki/(More-than)-one-million-requests-per-second-in-Node.js

[joshuafcole]

This is likely worth looking into down the road, but right now our primary bottleneck is our evaluation strategy. We're currently working on that since we expect it to have large returns for improving performance.

In the interim, if any sufficiently interested users feel passionate about this please feel free to port master to uWebSockets and provide some perf info so we can see how big the change is.