gRPC (gRPC Remote Procedure Calls) is an open-source remote procedure call (RPC) system initially developed at Google. It uses Protocol Buffers as the interface definition language (IDL) and data serialization format. gRPC enables applications to communicate with each other over a network, offering advantages like performance, scalability, and bidirectional streaming. In this article, we will explore how to integrate gRPC into a Spring Boot eCommerce application, like Amazon, using a step-by-step approach, sequence diagrams, and code examples.