Each microservice has a public endpoint, with a different TCP port for each microservice. A direct client-to-microservice communication architecture could be good enough for a small microservice-based application.
Advantages
- Simple to develop, therefore the final solution is less complex
- Fast processing and shorter response times
Disadvantages - The client apps are coupled to the internal microservices.
- A single page/screen in the client app might require several calls to multiple services.
- Every microservice needs to be concerned with security issues
Apps connect to a single endpoint, the API Gateway, that's configured to make requests to individual microservices or multiple microservices by asynchronous message-based communication. Therefore, the API gateway sits between the client apps and the microservices. It can act as a reverse proxy, making requests from clients to services, and it can also provide other cross-cutting features such as authentication, SSL termination, and cache.
Advantages
- Insulates the clients from how the application is partitioned into microservices
- Insulates the clients from the problem of determining the locations of service instances
- Provides the optimal API for each client
- IP allowlisting
- Authentication and authorization Disadvantages
- Single point of failure
- Longer response time than direct client-to-microservice communication
