How does one choose to architect a system that has a Microservice / REST API endpoints? There are many solutions out there. Some are better than others. Should state be held in a server side component, or externally? Generally we are told this is not a good practice for a Cloud Native system, when the 12-factor guidelines seem to be all about stateless containers, but is it? It’s unclear and this confusion may lead to poor technology stack choices that are impossible or extremely hard to change later on as your system evolves in terms of demand and performance.

While stateless systems are easier to work with, the reality is that we live in a stateful world, so we have to handle the state of data accordingly to ensure data integrity beyond securing it.

We will examine and demonstrate the fundamentals of a Cloud Native system with Stateful Microservices that’s built with Open Liberty in Kubernetes:

* Microservices/REST API – Options to use when running your apps in the JVM. Use of the Saga Programming Pattern, and the Long-Running Action feature of MicroProfile

* Concurrency – how to take advantage of multi-core CPUs and clustered distributed systems

* Stateful vs Stateless - while stateless apps are easier to implement, the bulk of the apps in production are stateful which involve a higher level of complexity and risk, especially when data would need to travel across multiple machines and network boundaries

* Deployment – how about containerization and orchestration using Kubernetes?