alt Hacker NewsBut a monorepo wouldn't make any of that easier.
You have to make the change to service A and B, and then test both and deploy both. You haven't saved any time or effort in a monorepo.
A library needs updating, you still have to update it and then test and deploy every service that relies on it independently. Again you haven't saved any time or effort. In fact you've made it worse, because if those services are maintained by different people, you just forced them to test and deploy on your timeline and priority, not theirs. You actually made the coordination problem worse.
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The big thing about monorepos in this case is making a change atomic across a set of projects. Multirepos can't do this 99% of the time and often add a lot more procedure to something close. It's inherently async.
I haven’t worked at a Big Tech monorepo place, but I hope/assume that in the service dependency case, you would touch both in one changeset and the deploy tooling understands the dependency tree and orders the deployments correctly. Without that i agree its the polyrepo approach just with all PRs in the same repo instead of multiple.
In the library scenario, I know tooling like bazel ensures that’s one changeset, not 3+. Tests run for both the changed library and all consumers of it in the same pass. You’re right that it might loop in others for review who weren’t expecting it, but i think that’s the same in a polyrepo approach.