gRPC

gRPC uses http/2 by default and is faster than REST. When using protocol buffers for encoding, the information comes on and off the wire much faster than JSON. Latency is an important factor in distributed systems. JSON encoding creates a noticeable factor of latency. For distributed systems and high data loads, gRPC can actually make an important difference. Other than that, gRPC supports multiple calls via the same channel and the connections are bidirectional. A single connection can transmit requests and responses at the same time. gRPC keeps connections open to reuse the same connection again which prevents latency and saves bandwidth.

gRPC empowers better relationships between clients and servers. The rules of communication are strictly enforced. That is not the case in REST calls, where the client and the server can send and receive anything they like and hopefully the other end understands what to do with it. In gRPC, to make changes to the communication, both client and server need to change accordingly. This prevents mistakes specially in microservice architectures.

gRPC requests are re-using the same context and can be tracked or traced across multiple service boundaries. This helps to identify slow calls and see what is causing delays. It is possible to cancel requests which cancels them on all involved services.

gRPC has been evolving and has become the best option for communication between microservices because of its unmatched performance and its polyglot nature. One of the biggest strengths of microservices is the freedom of programming languages and technologies. By using gRPC we can leverage all the advantages of strictly enforced communication standards combined with freedom of choice between different programming languages - whichever would fit best.