In a recent implementation of a large core banking project where we were breaking away from monolithic architecture to microservice based one we faced a situation where customer wanted to have a single repository of user and role management. Since Micro service based architecture talks about individual entities for multiple product suite it was mandatory to maintain individual user base.

Based on the customer feedback, we had to come up with an unique design of single user base and replicating them to different core of the product.

Another example was true layering of custom build for making software kernel upgrade proof.