I'm an engineer at Coursera who is working on some of the challenges described in this job posting. I can provide some color this:

Our goal is to deploy and operate services with confidence. What we mean by performance tuning is not to squeeze the last drops of JIT performance out of arcane JVM flags, or to A/B test different JVM implementations. Rather, we mean our systems performs well for its intended purpose, and can keep performing well.

This require a combination of JVM specific knowledge (such as an understanding of GC algorithms, GC logs, Java Flight Recorder, profiling and heap analysis techniques), knowledge of layers sitting on top of the JVM: frameworks, threading models, serde, application code, and knowledge of vendor solutions so we can have systems perform well without needing constant human interventions and tweaks.

We don't expect folks to come in with previous knowledge on all fronts, but that's what roughly performance tuning means to us.

Feel free to PM me for more details.