Are you expected to know the product codebase fairly well, debug complex bugs on the fly when paged, and push fixes out in a short window of time (<1 hour)? Also interested in what tooling you develop for the use by other SREs (if you can share).
In my case:
* I have a good in-depth knowledge of one product I'm oncall for. My team may implement some design changes required (ex: for scaling) and I contribute code to this project.
* I have shallow knowledge of 2 other products, I'm trained at identifying a trigger that causes an outage and mitigate it (common mitigations are: move traffic, increase quota temporarily, rollback a release). If I can't solve an incident without in-depth knowledge of these products, I escalate to the devteam, and they will be responsible for root-causing.
A mitigation that requires a patch, cherry pick and rollout would be a terrible (and risky) thing to do, so I'd rather find any alternative first.