Install @grpc/grpc-js and @grpc/proto-loader. Define service methods in a .proto file. Bootstrap the microservice with Transport.GRPC pointing to the proto file. Decorate handler methods with @GrpcMethod('ServiceName', 'MethodName') where the names must exactly match the proto service and rpc definitions.

Proto definition, gRPC microservice, and client

gRPC setup rules:

1
package in options must match the package statement in the .proto file.
2
@GrpcMethod('ServiceName', 'MethodName') — both names must exactly match the proto definitions.
3
The proto file path must resolve correctly at runtime — use __dirname and join() for portability.
4
Client uses getService<ServiceClient>('ServiceName') to get a typed client proxy for calling remote methods.
5
Share the .proto file between services via a shared npm package or a git submodule for consistency.

Difficulty: 6/10

Topics: gRPC server configuration, proto file integration, NestJS microservice transport

Scenario Questions

0-2 years experience

1
Walk me through the steps you'd take to add a gRPC server to a new NestJS microservice.
2
If you have a .proto file defining a UserService, how would you generate and use the client in a NestJS module?
3
What happens if the proto file and the generated TypeScript definitions get out of sync? How would you notice and fix it?

2-5 years experience

1
We tried to call a gRPC method from another NestJS service and got a deadline exceeded error. What could be causing this, and how would you troubleshoot?
2
Explain how you would configure NestJS to support both gRPC and HTTP transports for the same service, and why you might want to.
3
When adding versioning to your gRPC APIs, what changes are needed in the NestJS setup and the proto definitions?

5-8 years experience

1
Describe how you would implement server‑side streaming for a large data export in NestJS using gRPC, and what performance considerations you’d keep in mind.
2
How would you secure gRPC communication between NestJS microservices in a production environment?
3
If you need to add request/response logging and error handling across all gRPC calls, where would you place interceptors in NestJS, and what trade‑offs exist?

8+ years experience

1
Our platform currently uses REST for inter‑service communication, but we want to migrate to gRPC for performance. How would you plan the migration across multiple NestJS teams while minimizing disruption?
2
Discuss the pros and cons of using a service mesh (e.g., Istio) with NestJS gRPC microservices versus handling load balancing and retries in the application layer.
3
How would you design a versioning strategy for gRPC APIs that need to evolve over years, ensuring backward compatibility and smooth rollout across many services?

Follow-up Questions

❓Can you show a minimal NestJS module snippet that registers the gRPC server?
❓What are common pitfalls when the generated protobuf types get out of sync with the service implementation?
❓How do you unit‑test a gRPC handler in NestJS?