> I’m not begging the question. I’m simply stating what loose coupling looks like and the blog post is precisely the problem of tight coupling.

But it is not! They were updating dependencies and deploying services separately, and this led to every one of 140 services using a different version of "shared-foo". This made it cumbersome, confusing and expensive to keep going (you want a new feature from shared-foo, you have to take all the other features unless you fork and cherrypick on top, which makes it a not shared-foo anymore).

The point is that true microservice approach will always lead to exactly this situation: a) you either do not extract shared functions and live with duplicate implementations, b) you enforce keeping your shared dependencies always on very-close-to-latest (which you can do with different strategies; monorepo is one that enables but does not require it) or c) you end up with a mess of versions being used by each individual service.

The most common middle ground is to insist on backwards compatibility in a shared-lib, but carrying that over 5+ years is... expensive. You can mix it with an "enforce update" approach ("no version older than 2 years can be used"), but all the problems are pretty evident and expected with any approach.

I'd always err on the side of having a capability to upgrade at once if needed, while keeping the ability to keep a single service on a pinned version. This is usually not too hard with any approach, though monorepo makes the first one appear easier (you edit one file, or multiple dep files in a single repo): but unless you can guarantee all services get replaced in a deployment at exactly the same moment — which you rarely can — or can accept short lived inconsistencies, deployment requires all services to be backwards compatible until they are all updated with either approach).

I'd also say that this is still not a move to a monolith, but to a Service-Oriented-Architecture that is not microservices (as microservices are also SOA): as usual, the middle ground is the sweet spot.