[GeneralMayhem]

Internal and external have wildly different requirements. Google internally can't update a library unless the update is either backward-compatible for all current users or part of the same change that updates all those users, and that's enforced by the build/test harness. That was an explicit choice, and I think an excellent one, for that scenario: it's more important to be certain that you're done when you move forward, so that it's obvious when a feature no longer needs support, than it is to enable moving faster in "isolation" when you all work for the same company anyway.

But also, you're conflating code and services. There's a huge difference between libraries that are deployed as part of various binaries and those that are used as remote APIs. If you want to update a utility library that's used by importing code, then you don't need simultaneous deployment, but you would like to update everywhere to get it done with - that's only really possible with a monorepo. If you want to update a remote API without downtime, then you need a multi-phase rollout where you introduce a backward-compatibility mode... but that's true whether you store the code in one place or two.

[vlovich123]

The whole premise of microservices is loose coupling - external just makes it plainly obvious that it’s a non starter. If you’re not loosely coupling you can call it microservices but it’s not really.

Yes I understand it’s a shared library but if updating that shared library automatically updates everyone and isn’t backward compatible you’re doing it wrong - that library should be published as a v2 or dependents should pin to a specific version. But having a shared library that has backward incompatible changes that is automatically vendored into all downstream dependencies is insane. You literally wouldn’t be able to keep track of your BOM in version control as it obtains a time component based on when you built the service and the version that was published in the registry.

[GeneralMayhem]

> if updating that shared library automatically updates everyone and isn’t backward compatible you’re doing it wrong that library should be published as a v2 or dependents should pin to a specific version

...but why? You're begging the question.

If you can automatically update everyone including running their tests and making any necessary changes to their code, then persisting two versions forever is a waste of time. If it's because you can't be certain from testing that it's actually a safe change, then fine, but note that that option is still available to you by copy/pasting to a v2/ or adding a feature flag. Going to a monorepo gives you strictly more options in how to deal with changes.

> You literally wouldn’t be able to keep track of your BOM in version control as it obtains a time component based on when you built the service

This is true regardless of deployment pattern. The artifact that you publish needs to have pointers back to all changes that went into it/what commit it was built at. Mono vs. multi-repo doesn't materially change that, although I would argue it's slightly easier with a monorepo since you can look at the single history of the repository, rather than having to go an extra hop to find out what version 1.0.837 of your dependency included.

> the version that was published in the registry

Maybe I'm misunderstanding what you're getting at, but monorepo dependencies typically don't have a registry - you just have the commit history. If a binary is built at commit X, then all commits before X across all dependencies are included. That's kind of the point.