Custom cache keys in NestJS - Mini Project: Build & Apply

Custom Cache Keys in NestJS

📖 Scenario: You are building a NestJS service that caches user data. To improve cache management, you want to create custom cache keys based on user IDs.

🎯 Goal: Build a NestJS service that uses a custom cache key function to store and retrieve cached user data.

📋 What You'll Learn

Create a NestJS service with a method to get user data.

Add a custom cache key function that uses the user ID.

Use the cache interceptor with the custom cache key function.

Ensure the cache key is unique per user ID.

💡 Why This Matters

🌍 Real World

Custom cache keys help store and retrieve cached data uniquely, improving performance and reducing redundant data fetching in web applications.

💼 Career

Understanding custom cache keys in NestJS is useful for backend developers working on scalable and efficient server-side applications.

1

Create a NestJS service with a method to get user data

Create a NestJS service class called UserService with a method getUserData that takes a parameter userId and returns a string `User data for ${userId}`.

NestJS

export class UserService {
  // Create getUserData method here
  // Your code here
}

Need a hint?

Define a class with a method that returns a template string using the userId parameter.

2

Add a custom cache key function using the user ID

Create a function called customCacheKey that takes context as a parameter and returns a string cache key in the format `user-cache-${userId}`. Extract userId from context.args[0].

NestJS

export class UserService {
  getUserData(userId: string): string {
    return `User data for ${userId}`;
  }
}

// Create customCacheKey function here
// Your code here

Need a hint?

Use context.args[0] to get the userId and return a string with that ID.

3

Use the cache interceptor with the custom cache key function

In a NestJS controller class called UserController, create a method getUser that takes userId as a parameter and calls userService.getUserData(userId). Use the @UseInterceptors(CacheInterceptor) decorator with options to set cacheKeyFactory to customCacheKey. Inject UserService in the constructor.

NestJS

export class UserService {
  getUserData(userId: string): string {
    return `User data for ${userId}`;
  }
}

function customCacheKey(context: any): string {
  const userId = context.args[0];
  return `user-cache-${userId}`;
}

// Create UserController with getUser method and cache interceptor
// Your code here

Need a hint?

Use @Controller, inject UserService, and decorate getUser with @UseInterceptors(CacheInterceptor).

4

Configure the cache interceptor to use the custom cache key factory

Modify the @UseInterceptors(CacheInterceptor) decorator on UserController to pass options with cacheKeyFactory set to customCacheKey.

NestJS

import { Controller, Get, Param, UseInterceptors, CacheInterceptor } from '@nestjs/common';

export class UserService {
  getUserData(userId: string): string {
    return `User data for ${userId}`;
  }
}

function customCacheKey(context: any): string {
  const userId = context.args[0];
  return `user-cache-${userId}`;
}

// Modify the UseInterceptors decorator to use cacheKeyFactory
@UseInterceptors(CacheInterceptor)
@Controller('users')
export class UserController {
  constructor(private readonly userService: UserService) {}

  @Get(':userId')
  @UseInterceptors(CacheInterceptor)
  getUser(@Param('userId') userId: string): string {
    return this.userService.getUserData(userId);
  }
}

Need a hint?

Pass an options object with cacheKeyFactory: customCacheKey to the @UseInterceptors decorator.