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Spring / Spring gRPC Interview Questions

What are the four types of service methods gRPC supports?

A gRPC service method can be declared as one of four call shapes in the .proto file:

  • Unary RPC - one request, one response, like a normal method call.
  • Server streaming RPC - one request, a stream of responses.
  • Client streaming RPC - a stream of requests, one final response.
  • Bidirectional streaming RPC - both sides send independent streams of messages over the same connection.

The shape is declared with the stream keyword on the request and/or response type in the .proto definition, and the generated Java stub method signature changes accordingly (a simple return value for unary, versus StreamObserver-based signatures for the streaming variants).

flowchart LR
  A[Unary: 1 req -> 1 res] 
  B[Server streaming: 1 req -> N res]
  C[Client streaming: N req -> 1 res]
  D[Bidirectional: N req -> N res]
Which RPC type sends a single request and receives a single response?
Which RPC type allows both client and server to send independent streams over one connection?

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