Tag Archives: micro-apps

How big should a micro-service be?

SRP and my Head

Many years ago, whilst working at an Investment Bank with a number of ThoughtWorks colleagues, we were thinking about how big objects should be. Obviously as developers we were thinking in terms of the Single Responsibility Principle, Open-Closed Principle and Separation of Concerns.

I came up with a simple heuristic. Simply stated, an object should be no bigger than the size of my head when pressed up against the monitor – basically a screenful of code. Now, I have a fairly big head (but thats ok, cos there ain’t much inside it) so your mileage may vary.

The reason I bring this up is because I’ve been speaking at a few conferences recently on the topic of Micro Services, and the following question is often asked:

“How big should an application be?”
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