I'm called in to consult on a performance problem on a scaled service. Team was load testing their code and seeing low throughput: Me: so you have an in-memor

I'm called in to consult on a performance problem on a scaled service. Team was load testing their code and seeing low throughput: Me: so you have an in-memory cache, right? Them: yes! Me: what is the TTL? Them: Oh, it's not set, oops. Here, let's set it to 1 minute. Hey look, the performance went way up! Me: okay, great. When you say 1 minute, do you mean 60 seconds? Them: uh...wait...uh....oh, the unit is seconds. Wait, why is the performance so good with a 1 second TTL? Me: What's your load test? Them: We crank 1M TPS fetching the same 30 items over and over. Me: .... I totally agree about the power of profiling but profiling without understanding would not have helped this team.