Just use a monorepo
IMO the biggest drawback to a monolith, maybe beyond those listed, is losing the 1-1 mapping of changes to CI to releases. If you know "this thing is broken", the commit log is a fantastic resource to figure out what changed which may have broke it. You submit a PR, and CI has to run; getting most CI platforms cleanly configured to, say, "only run the user-service tests if only the user-service changes" isn't straightforward. I understand there are some tools (Bazel?) which can do it, but the vast, vast majority of systems won't near-out-of-the-box, and will require messy pipelines and shell scripts to get rolling.There's also challenges with local dev tooling. Many VSCode language extensions, for example, won't operate at their best if the "language signaler" file (e.g. package.json for JS) isn't in the root of the repo; from just refusing to function, to intellisensing code in another project into this one, all manner of oddities.Meanwhile; I don't think the purported advantages are all that interesting. Being able to write the blog post and make the change in the same PR? I've never been in a role where we'd actually want that; we want the change running silently in prod, publish the blog post, flip a feature flag or A/B test proportions. Even an argument like "you can add schemas and the API changes in one go"; you can do that without a "monorepo", just co-locate your schemas with the API itself, this isn't controversial or weird, this is how everywhere I've worked operates.None of that is to even approach the scale challenges that come with monorepos at even reasonable sizes; which you can hit pretty quickly if you're, say, vendoring dependencies. Trying to debug something while the Github or Bitbucket UI is falling over because the repo is too large, or the file list is too long, isn't fun.I'm not going to assert this is a hill I would die on, but I'm pretty staunchly in the "one service, for one deployment artifact, for one CI pipeline, for one repo" camp.