[achiang]

Google SRE here.

Point of clarification on "losing skills" by not being oncall enough.

Google designs its SRE teams to scale sublinearly to the service, which means we're often responsible for entire portfolios, not just a single service.

It's common for individuals to be SMEs on a subset of the portfolio, as the focus of their coding projects.

Obviously the rest of the portfolio is also undergoing continuous change, and so to remain a broadly effective oncaller across the entire portfolio, you need regular production exposure to the parts you interact with less frequently.

Those are the specific bits that get rusty with disuse.