gRPC transport in NestJS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this NestJS gRPC service call?

Consider a NestJS gRPC service with this method:

async getHello(): Promise<{ message: string }> { return { message: 'Hello from gRPC!' }; }

If a client calls getHello, what will the client receive?

NestJS

async getHello(): Promise<{ message: string }> { return { message: 'Hello from gRPC!' }; }

A A JSON object with a 'message' property containing 'Hello from gRPC!'

B A plain string 'Hello from gRPC!'

C An error because gRPC does not support returning objects

D An empty response with no data

💡 Hint

gRPC methods typically return objects matching the protobuf message structure.

The method returns an object with a 'message' property. The client receives this object serialized by gRPC.

📝 Syntax

intermediate

Which option correctly configures a NestJS microservice to use gRPC transport?

Choose the correct code snippet to create a NestJS microservice using gRPC transport with package 'hero' and proto file 'hero.proto'.

A app.createMicroservice({ transport: Transport.GRPC, options: { package: 'hero', protoPath: 'hero.proto' } });

B app.connectMicroservice({ transport: Transport.GRPC, options: { package: 'hero', protoPath: 'hero.proto' } });

C app.connectMicroservice({ transport: Transport.TCP, options: { package: 'hero', protoPath: 'hero.proto' } });

D app.createMicroservice({ transport: Transport.HTTP, options: { package: 'hero', protoPath: 'hero.proto' } });

💡 Hint

Use connectMicroservice with Transport.GRPC for gRPC microservices.

Only option B uses connectMicroservice with the correct transport and options for gRPC.

🔧 Debug

advanced

What error occurs if the protoPath is incorrect in NestJS gRPC microservice config?

If you configure a NestJS gRPC microservice with a wrong protoPath that does not exist, what error will you see when starting the app?

A SyntaxError: Unexpected token in proto file

B TypeError: Cannot read property 'package' of undefined

C Error: ENOENT: no such file or directory, open 'wrong.proto'

D No error, the app starts normally

💡 Hint

Check the file path carefully when loading proto files.

If the proto file path is wrong, Node.js throws a file not found error (ENOENT).

❓ state_output

advanced

What is the value of the variable after this gRPC client call in NestJS?

Given this client call:

const response = await client.send<{ message: string }>('getHello', {}).toPromise();

What is the value of response.message if the server returns { message: 'Hi there!' }?

NestJS

const response = await client.send<{ message: string }>('getHello', {}).toPromise();

A null

B An error is thrown

C undefined

D 'Hi there!'

💡 Hint

The client receives the server's response object.

The response variable holds the object returned by the server, so response.message is 'Hi there!'.

🧠 Conceptual

expert

Which statement best describes the role of protobuf in NestJS gRPC transport?

Choose the most accurate description of how protobuf works with NestJS gRPC transport.

A Protobuf defines the message and service structure used to serialize and deserialize data between client and server.

B Protobuf is a database technology used to store gRPC messages persistently.

C Protobuf is a UI framework for building gRPC client interfaces.

D Protobuf automatically generates REST endpoints from gRPC services in NestJS.

💡 Hint

Think about what protobuf files describe in gRPC communication.

Protobuf files define the structure of messages and services so gRPC can serialize and deserialize data correctly.