Cache decorators in NestJS - Mini Project: Build & Apply

Using Cache Decorators in NestJS

📖 Scenario: You are building a simple NestJS service that fetches user data. To improve performance, you want to cache the results of the data fetching method.

🎯 Goal: Build a NestJS service that uses the @Cacheable() decorator to cache the result of a method that returns user information.

📋 What You'll Learn

Create a NestJS service class named UserService.

Add a method getUser() that returns a user object with id and name.

Add a cache configuration variable cacheTTL set to 30 seconds.

Use the @Cacheable() decorator on getUser() with the ttl set to cacheTTL.

Ensure the service is ready to be used in a NestJS module.

💡 Why This Matters

🌍 Real World

Caching is used in real-world applications to speed up repeated data fetching and reduce load on databases or APIs.

💼 Career

Understanding cache decorators in NestJS is important for backend developers to optimize performance and scalability of server applications.

1

Create the UserService class with getUser method

Create a NestJS service class called UserService with a method getUser() that returns an object { id: 1, name: 'Alice' }.

NestJS

export class UserService {
  // Your code here
}

Need a hint?

Define a class named UserService and add a method getUser() that returns the user object.

2

Add cacheTTL configuration variable

Inside the UserService class, add a variable cacheTTL and set it to 30 to represent 30 seconds.

NestJS

export class UserService {
  cacheTTL = 30;

  getUser() {
    return { id: 1, name: 'Alice' };
  }
  // Your code here
}

Need a hint?

Add a class property cacheTTL and assign it the number 30.

3

Import and apply @Cacheable decorator with ttl

Import @Cacheable from @nestjs/cache-manager and apply it as a decorator on the getUser() method. Set the decorator option ttl to the class variable cacheTTL.

NestJS

import { Cacheable } from '@nestjs/cache-manager';

export class UserService {
  cacheTTL = 30;

  @Cacheable({ ttl: this.cacheTTL })
  getUser() {
    return { id: 1, name: 'Alice' };
  }
  // Your code here
}

Need a hint?

Import @Cacheable and decorate getUser() with @Cacheable({ ttl: 30 }). Use the number 30 directly for simplicity.

4

Export UserService for module use

Add export keyword before the UserService class declaration to make it available for import in other modules.

NestJS

import { Cacheable } from '@nestjs/cache-manager';

// Your code here

export class UserService {
  cacheTTL = 30;

  @Cacheable({ ttl: 30 })
  getUser() {
    return { id: 1, name: 'Alice' };
  }
}

Need a hint?

Make sure the class declaration starts with export class UserService.