I use Go and it gives me a good sweet spot between cost and perf.
I’m nowhere close to performance requirements of Pinterest. But my auth service runs on a single 1vcpu, 512mb ram, and 10gb ssd. I use leveldb and swap on the 10gb. I’ve benchmarked it to handle 8-9k rps while delivering 150ms max response time. Not bad for a few bucks a month.