Could you explain the concept of API composition in the context of microservices?

API composition in the context of microservices is an approach where a separate service (composition layer) aggregates data and functionality from multiple microservices, providing a unified API for the client.

Instead of the client directly calling multiple microservices, the composition service aggregates responses, processes the merging logic, and returns a single result. This simplifies the client side and reduces the number of network calls.

Example: there are microservices for users, orders, and payments. The API composition creates a service that, upon a client's request, gathers data from all three services and returns a combined information.

This approach helps to:

• Hide the complexity of the internal architecture from the client.
• Centralize the logic of data aggregation and transformation.
• Improve performance by reducing the number of requests.

In Python, this can be implemented using HTTP requests to microservices and merging results, for example, using requests and asynchronous libraries.