Ask HN: Querying across microservices

Microservices seem to increase developer productivity by letting devs work independently on different parts of an app at their own pace. However this implies that any state managed by a microservice is often isolated from other microservices, i.e. each microservice has a database of its own.

In theory, then, a query across microservices would be challenging. One could encounter data interdependence issues across microservices. Further, querying across microservices using joins and aggregations could require complex application level code to realize.

So, HN, does anyone encounter problems with querying across microservices today? And if so how do they solve these problems?