With a service of this size creating a copy of prod is a non-trivial problem, and there are classes of bugs that will only manifest against prod data. A pristin

With a service of this size creating a copy of prod is a non-trivial problem, and there are classes of bugs that will only manifest against prod data. A pristine, miniature pretend-prod just isn't that useful. What I've seen work in the past is that you develop your changes locally, run a local instance of whatever service you're changing, but local instance is backed by stateful layers in prod. Feature flags are ingrained in the culture, and you'll be expected to do things like gate your code to some small set of users at first. Employees are a good option, or test users created in prod if you're especially wary of your changes. I only know of this leading to one SEV, where the feature flags broke in such a way that everything was suddenly enabled for everyone.