How to organize data transfer from three microservices (products, prices, orders) in a microservice architecture?

In microservice architecture, to transmit data to the client from multiple microservices (e.g., products, prices, orders), one of the following approaches is often used:

1. API Gateway / Aggregator

   • A separate service (API Gateway) is created, which receives requests from the client.
   • It communicates with microservices for products, prices, and orders, gathers data, and forms a single response.
   • The client receives aggregated data with a single request.

2. Backend for Frontend (BFF)

   • A specialized service tailored for a specific client (web, mobile).
   • Performs aggregation and transformation of data from different microservices.

3. GraphQL

   • Using a GraphQL server that internally communicates with various microservices.
   • The client requests exactly the data it needs in one request.

4. Event-driven / CQRS

   • Microservices publish events about changes.
   • A specialized service collects and aggregates data into a separate storage for quick reading.

The choice depends on performance requirements, complexity, and data update frequency. In practice, API Gateway or BFF are often used for simplicity and centralized management.