System Decomposition From Business Requirements To Microservices

[JGeek]

Hello Everyone, 

I am looking for advice on how to decompose an application into microservices from business requirements. We are working on a green field project that needs to be decomposed into microservices since independent evolution of services is a key requirement.  

I came across few decomposition techniques including "Functional decomposition using use case specifications", "Data driven decomposition using data flow diagrams with database per service being the key principle", "Message first approach from the book The Tao Of Microservices". I am mid-way in applying these techniques to our application and looking out for advice from someone who has done this exercise.  

We have a domains diagram from our product managers that shows different components of the system with some marked as "independent offerings". The components are depicted as processes which have their functionalities noted as sub-processes. There is also an entity relationship diagram that displays relationships between business entities. 

With the use case specification being worked up in parallel, I am trying to build up level-0 and level-1 DFD diagrams taking certain assumptions. Any guidance from someone who has done this system decomposition exercise would be really appreciated.  

Thanks. 

[Jakub Pośpiech]

I highly recommend Event Storming.

Best Regards

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[Ben Kloosterman]

You didnt say DDD or Event driven ?

Start with CRUD master data services which should be simple and easy to build upon  , then start adding core business events etc 

" There is also an entity relationship diagram that displays relationships between business entities. " This is a red flag  in micro services and esp event driven ones some of these solutions dont match well to these well behaviour vs data  view of the world. 

Certainly group the master data services according to traffic between entities use a lot oo get bymultipleids calls 

Ben

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