How to handle caching and database management in microservices architecture?

Question

I'm getting into microservices architecture and there are some issues which are badgering me. The main advantage of microservices is scalability. Let's say that I have service and I'm running 1-n instances of there services.

1. In case of spring boot application, we have cool easy to implement cache mechanism, but our instances will be not aware of each other's data what is the common solutions, or simple alternative for such cache?

2. Some of the services can use the same database with the second-level cache. How can services communicate with each other in such case?

Please provide any good materials for "easy switch" from monolith app to microservices approach.

• Alexander: If scalability is a serious issue (in most use cases, it's not), then a shared cache, used by all nodes, isn't feasible. It's a single-point of failure, and is not distributable. If your application's needs can be met by a single load balancer, and a single cache server, then Greg's comment applies
• Erik Eidt: see does each microservice really need its own database?
• kingkong: @ErikEidt separating microservices is not an issue for me. In my thinking, I'm more focused on the relationship between same service INSTANCES. Let's imagen one service eg. User service that instances will have different states of the same object.
• Erik Eidt: The concern you're talking is about scaling the underlying implementation of one microservice, rather than an architecture of separate microservices.

Answer 1

Could be as easy as putting your micro services behind load balancers, and then put a cache server in front of the load balancer. Cache by request URL. This is just basic horizontal scaling and caching. The rules are the same for a micro service and a monolith.

• kingkong: I do understand URL request caching and that is fine. But I'm trying to more concentrate on a single instance of microservices. If I'm using such technology as spring cache, in service it makes my service stateful isn't?