Core capabilities are those components generally packaged inside a single microservice. For example, let's take an Order microservice. The Order microservice will have two key deployable parts, order.jar developed using Spring Boot and its own database--Order DB. The order.jar will encapsulate service listeners, libraries required for execution, service implementation code, and service APIs or endpoints, and Order DB stores all data required for Order service. Smaller microservices only require these core capabilities.
Gartner named this as inner architecture and the capabilities outside of this core as outer architecture.
In Chapter 3, Building Microservices with Spring Boot, we discussed the implementation of core capabilities using Spring Boot.
The core capabilities depicted in the capability model are explained in the following section.