I'm a database guy, so the question I get from clients is, "We're thinking about breaking up our monolith into a bunch of microservices, and we want to use best-of-breed persistence layers for each microservice. Some data belongs in Postgres, some in DynamoDB, some in JSON files. Now, how do we do reporting?" Analysts expect to be able to connect to one system, see their data, and write queries for it. They were neve…
One of the key concepts in microservice architecture is data sovereignity. It doesn't matter how/where the data is stored. The only thing that cares about the details of the data storage is the service itself. If you need some data the service operates on for reporting purposes, make an API that gets you this data and make it part of the service. You can architect layers around it, maybe write a separate service that aggregates data from multiple other services into a central analytics database and then reporting can be done from there or keep requests in real time, but introduce a caching layer or whatever. But you do not simply go and poke your reporting fingers into individual service databases. In a good microservice architecture you should not even be able to do that.