There is a system A and B which should communicate, usually via an API from system to system. To Have no coupling between A and B (A should not have implicit knowlegde of what B needs to process and vice versa) there is a "mediation service" C which is responsible for translating stuff from A to B. So C has implicit knowledge of both systems.

Since C is some kind of extra service i don't know if there should be a strong coupling between A and C and B and C or if the coupling between all involved service should be loosely every time.

For example:

Loosely coupled: A wants to communicate with B over C ... C is translating the stuff from A and sends it to the API of B ... B "translates" the stuff again to its own internal required format.

Tightly coupled: C is directly transforming the data in the format that B requires to process. C therefore has direct influence of internal processes of B

Going with a "loosely coupled" approach it makes no sense for me why using a "mediation service" at all, it just raises the complexity since there is now some extra translation layer ... or do i miss something?

So my question: Is it common that services which are not living in the same space are tightly coupled? Or is this usually a conceptual mistake?


  • The C service you're describing is (most) often called an adapter. It's sole purpose is to decouple 2 parties, so talking about tight or loose coupling makes little sense, to be honest. – Shadows In Rain Apr 19 at 9:26
  • What to talk about else in your opinion? – Jim Panse Apr 19 at 9:53
  • The way your question is worded suggests the lack of research. Mediators, adapters, orchestrators and the likes provide decoupling by design. It's definitely their job to implement all the required plumbing. – Shadows In Rain Apr 19 at 10:54
  • But the "C" service is no adapter ... since it does not belong to one of the communicating services. So i think you didn't got the question right. – Jim Panse Apr 19 at 14:30
  • Yes, that was a mistake on my part, that's why I switched the attention to the whole group of decoupling patterns rather than insisting on the adapter. The point stands, though. – Shadows In Rain Apr 19 at 14:37

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