Microservices Versus APIs

Microservices Are Not Just Smaller APIs

Microservices are not just smaller replacements for the APIs of the old days. Microservices provide the implementation of your system, while APIs should still be the outward-facing interface of a system.

Figure 3–5. Relationship between microservices and APIs

Keep Microservices Unaware of Each Other

Avoid microservices directly “knowing” about each other and directly calling each other via synchronous interfaces. Instead, try to orchestrate processes involving multiple microservices in the API layer. If this is not possible, consider using asynchronous inter‐ faces between microservices where an upstream microservice publishes data to an event log (e.g., Kafka) and a downstream microservice can subscribe to that event log without the upstream microservice having tight coupling with the subscriber(s).



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