Replace json with ujson?

[dmargol1]

This is just a suggestion, but I've found around a 25% speed boost parsing responses using ujson in place of json.

[squeaky-pl]

This is trivial to do but I need to measure things myself. Also ujson is written in C which opens a possibility of calling it without usual Python call convention overhead.

[ludovic-gasc]

Do your homeworks, but I can confirm the suggestion og @dmargol1: We use that in FrameworkBenchmarks test suite.