I've worked with thousands of other employees on a single monolithic codebase, which was delivered continuously. There was no complex overhead.
The process went something like this:
1. write code
2. get code review from my team (and/or the team whose code I was touching)
3. address feedback
4. on sign-off, merge and release code to production
5. monitor logs/alerts for increase in errors
In reality, even with thousands of developers, you don't have thousands of merges per day, it was more like 30-50 PRs being merged per day and on a multi-million line codebase, most PR's were never anywhere near each other.
The process went something like this:
1. write code
2. get code review from my team (and/or the team whose code I was touching)
3. address feedback
4. on sign-off, merge and release code to production
5. monitor logs/alerts for increase in errors
In reality, even with thousands of developers, you don't have thousands of merges per day, it was more like 30-50 PRs being merged per day and on a multi-million line codebase, most PR's were never anywhere near each other.