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Comment by ajanuary | Hacker News Reader

The point is that the realities of not being able to deploy in lockstep erode away at a lot of the claimed benefits the monorepo gives you in being able to make a change everywhere at once.

If my code has to be backwards compatible to survive the deployment, then having the code in two different repos isn’t such a big deal, because it’ll all keep working while I update the consumer code.

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The point is atomic code changes, not atomic deployments. If I want to rename some common library function, it's just a single search and replace operation in a monorepo. How do you do this with multiple repos?

> If I want to rename some common library function, it's just a single search and replace operation in a monorepo. How do you do this with multiple repos?

Multiple repos shouldn't depend on a single shared library that needs to be updated in lockstep. If they do, something has gone horribly wrong.

They do, it's just instead of it being a library call it's a network call usually, which is even worse. Makes it nigh impossible to refactor your codebase in any meaningful way.

But if you need to rename endpoint for example you need to route service A version Y to compatible version in service B. After changing the endpoint, now you need to route service A version Z to a new version of service B. Am I missing something? Meaning that it doesn’t truly mater whether you have 1 repo, 2 repos or 10 repos. Deployments MUST be done in sequence and there MUST be a backwards compatible commit in between OR you must have some mesh that’s going to take care of rerouting requests for you.

You just deploy all the services at once, A B style. Just flip to the new services once they're all deployed and make the old ones inactive, in one go. Yes you'll probably need a somewhat central router, maybe you do this per-client or per-user or whatever makes sense.

So that's blue green with added version aware routing. What if you need to rollback? Good luck I guess.

You can do phased deployments with blue green, that's what we do. It depends on your application but ours has a natural segmentation by client. And when you roll back you just flip the active and passive again.

It doesn't need to, it's just much more convenient when you can do everything in a single commit.

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