You lost me at monorepo. That might work at a very small scale, but past that monorepos create more problems than they solve.
Saying that "monorepos are only good for large scale" is pure bullshit, and something that only someone very inexperienced would say.
I'm in a very small company (less than 10 devs) but we still use a monorepo, because we have a set of common libraries for all our products, and having a monorepo helps us update those libraries without breaking anything. On the other hand, some very large companies have tried and have failed.
Monorepos are just a tool. The implementation and the context matters more than anything else.
Monorepo forces the tough conversations. Maybe the organization should only use 1 language now. Maybe we should talk about code review policies and standardization of other processes since everyone is in the same bucket. Why can't everything just compile to 1 exe?
Another massive advantage with a monorepo if you use GitHub is that you now have 1 issue bucket that covers the entire enterprise. Linking issues to commits is super powerful when this technique covers 100% of your code and exists under 1 labeling scope.
You have to understand, many of us think microservices is a stupid idea, so the fact that the core of your argument is "monorepos make microservices difficult" is not an appealing argument.
If a monorepo puts a barrier in the way of turning everything into a microservice, then all the better, as far as I'm concerned.
You trade simplicity of having everything in one place vs. ability to independently version pieces at the cost of more complex tooling and build systems required to test.
Usually there's some sweet spot, but the answer isn't obvious and one isn't clearly better.
Container based solutions become harder? Again… build your artifacts and deploy all the containers you want? What is so hard about this?
Meanwhile, with multi-repo you lose out on a whole host of opportunities to robustly track dependencies and keep things up to date.
Everything in software is about dependencies, and monorepos are playing double or nothing with dependencies.
The issue with Monorepos is that they can amplify bad decisions and tech debt. Any bad decisions are magnified across the organization. But they definitely don't make it easier or harder to make that initial bad decision.
The upside is that dependencies are just there and not hidden behind interfaces.
The downside is that a bad dependency cannot be abstracted behind a micro-service interface. Once it's out in the wild it can do crazy things.
not liking microservices myself but - if I did this wouldn't it mean that the code in version 19 was now removed from the code in version 18 and back in git history making it more difficult to figure out just where things went wrong on a difficult little edge case.
git bisect helps to easily identify hard to find but reproducible bugs. Since we try to have small PRs once you found the breaking commit it is usually easy enough to the find the bug. Murphy and exceptions obviously apply.
We do not version our services in that sense. It's a monorepo after all.
We do have microservices.
We use kubernetes.
Deployment is a breeze. Only services with changes are actually deployed.
We do hourly deploys to production.
None of the issues you describe apply here and the monorepo works awesomely for us. This is a SaaS situation where all services making up that SaaS solution and that we host are in that monorepo.
YMMV if you are in a different situation such as having to ship versioned software for customers to self host/install for example. Our accompanying software that is usable in conjunction with the SaaS solution is not part of that Monorepo and each of those are versioned and deployed to various external marketplaces.
That is way different from providing v1 of your API and changes come out in v2 of the API while you also still provide v1 of the same API. You can (and we do) do that perfectly well with or without a monorepo. Mostly for the public API. Internal API's often don't need to do versioning and one can go with backwards compatible changes and/or rolling a change out over multiple commit deploy cycles.
Some of this will depend on your size I suppose. The larger the org, the more services etc. the more stable versioning I would suppose happening.
Which is why I said in my original comment this may work fine in a small environment, but it won’t scale well.
That said, we're not small either. In our niche, which you might recognize if I said more, we're the top solution customers choose (but I won't go into much more detail than that for obvious reasons).