Redis transport in NestJS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output when a NestJS microservice using Redis transport receives a message?

Consider a NestJS microservice configured with Redis transport that listens for a message pattern 'sum'. The handler adds two numbers from the data and returns the result.

What will be the response when the client sends {a: 5, b: 7}?

NestJS

import { Controller } from '@nestjs/common';
import { MessagePattern } from '@nestjs/microservices';

@Controller()
export class MathController {
  @MessagePattern('sum')
  sum(data: {a: number; b: number}): number {
    return data.a + data.b;
  }
}

A NaN

B 12

C undefined

D 57

💡 Hint

Think about what the sum function returns when given two numbers.

The handler receives the data object with properties a and b. It returns their sum, so 5 + 7 equals 12.

📝 Syntax

intermediate

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

Choose the correct way to create a NestJS microservice using Redis transport on port 6379.

NestJS

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';
import { Transport } from '@nestjs/microservices';

async function bootstrap() {
  const app = await NestFactory.createMicroservice(AppModule, {
    transport: Transport.REDIS,
    options: {
      host: 'localhost',
      port: 6379,
    },
  });
  await app.listen();
}
bootstrap();

A transport: Transport.REDIS, options: { host: 'localhost', port: 6379 }

B transport: 'redis', options: { url: 'redis://localhost:6379' }

C transport: Transport.REDIS, options: { url: 'redis://localhost:6379' }

D transport: Transport.TCP, options: { host: 'localhost', port: 6379 }

💡 Hint

NestJS Redis transport supports host and port in options.

Option A correctly uses Transport.REDIS and provides host and port, matching the official NestJS documentation for Redis transport.

🔧 Debug

advanced

Why does this NestJS Redis microservice fail to connect?

Given the following microservice bootstrap code, why does the connection to Redis fail?

NestJS

const app = await NestFactory.createMicroservice(AppModule, {
  transport: Transport.REDIS,
  options: {
    host: '127.0.0.1',
    port: 6380,
  },
});
await app.listen();

A Transport.REDIS does not accept 'host' and 'port' options, only 'url'.

B The host '127.0.0.1' is invalid for Redis connections.

C Redis server is not running on port 6380, causing connection failure.

D Missing await before app.listen() causes the failure.

💡 Hint

Check if Redis is running on the specified port.

The code tries to connect to Redis on port 6380, but Redis usually runs on 6379 by default. If Redis is not running on 6380, connection fails.

❓ state_output

advanced

What is the value of 'response' after sending a message to a Redis microservice?

In a NestJS client, a message with pattern 'multiply' is sent with data {x: 3, y: 4}. The microservice multiplies these numbers and returns the result.

What is the value of 'response' after awaiting the send call?

NestJS

const client = app.connectMicroservice({
  transport: Transport.REDIS,
  options: { url: 'redis://localhost:6379' },
});

await client.connect();
const response = await client.send('multiply', { x: 3, y: 4 }).toPromise();

A 12

B 7

C {x: 3, y: 4}

D undefined

💡 Hint

Think about what the microservice returns for the 'multiply' pattern.

The microservice multiplies x and y, so 3 * 4 equals 12. The client receives this value as the response.

🧠 Conceptual

expert

Which statement about Redis transport in NestJS microservices is TRUE?

Choose the correct statement about using Redis transport in NestJS microservices.

A Redis transport does not support pattern-based message routing.

B Redis transport requires manual handling of message serialization and deserialization by the developer.

C Redis transport can only be used for event-based fire-and-forget messaging, not request-response.

D Redis transport supports request-response messaging patterns with automatic message serialization.

💡 Hint

Consider how NestJS microservices handle messaging with Redis transport.

Redis transport in NestJS supports request-response messaging with automatic serialization and pattern-based routing, making option D true.