I'm an SRE at Google and when my friend asked what I do and I explained it to him he said

- "oh, so like QA in my company?"

I've asked what QA does at his company and well yeah, exactly. I've read the books and know about the SLA/SLO and honestly it doesn't make any sense for smaller companies with few services.

I code up alerts for various metrics, act upon said alerts, sometimes do the fixes my self if it's simple, otherwise just hand it off to devs by logging a bug. The remaining time I code tools for other SREs to use.