[richard_todd]

So their server needs are growing faster than their user-base to the extent that they considered switching languages. PHP didn't seem to perform much better, so they stuck with python and got a ~12% CPU usage improvement by moving to python3. It doesn't seem like a 12% one-time improvement actually solves the original problem, though. Perhaps pypy would have been better?

[williamstein]

Instagram also uses Cython a lot (so I've heard from a talk), so switching away from CPython might not provide as much of a speed up as one might otherwise expect, as one can get C levels of speed (and concurrency) with significant effort using Cython. Also, Cython and PyPy might not play so well together...