Stateful Microservices are commonly associated with dependencies on external data stores. These dependencies often introduce bottle necks in terms of performance and availability as the data source can act like a single point of failure. This problem has enhanced impact where multiple instances of a service co-exists at a given point. Maintaining high availability of the data store becomes expensive as the data grows. The following diagram illustrates a system with a centrally externalized data store:
Reliable data store (Problem)
A solution to this problem is to co-locate Microservice state with compute. This will reduce application's dependency on external data stores (such as cache) for frequently accessed data. Having the data stored on the same deployment instance as the consuming application also contributes positively to the system performance and negates the risk introduced by the data store being a single point of failure.
However, this introduces...