When should gRPC be used, and when REST in the context of microservices?

The choice between gRPC and REST in microservice architecture depends on performance requirements, data type, and compatibility.

Use gRPC if:

• High performance and low latency are needed, as gRPC uses HTTP/2 and a binary protocol.
• A strictly typed contract between services is required (protobuf).
• Support for streaming data in both directions is important.

REST is suitable if:

• Simplicity and broad compatibility are needed, as REST is based on HTTP/1.1 and the text-based JSON format.
• Clients may be heterogeneous and do not support gRPC.
• There are no strict performance or typing requirements.

Thus, gRPC is better for internal microservice interactions with high speed and typing requirements, while REST is suitable for external APIs and integrations with various clients.