Microservice Patterns - Hexagonal architecture

1. Inbound adapters:  handle requests from the outside by invoking the business logic
2. Outbound adapters:  invoked by the business logic and invoke external applications
3. Port: defines a set of operations and is how the business logic interacts with what’s outside of it 
1. inbound port:  an API exposed by the business logic, which enables it to be invoked by external applications. Ex. service interface / service public method
2. outbound port:  how the business logic invokes external systems. ex. repository interface, which defines a collection of data access operations