CacheModule setup in NestJS

Introduction

CacheModule helps your app remember data temporarily to make it faster. It avoids doing the same work again and again.

When you want to speed up responses by storing results of slow operations.

When you want to reduce load on a database by caching query results.

When you want to share cached data across different parts of your app.

When you want to set expiration times for data to keep it fresh.

When you want a simple way to add caching without writing complex code.

Syntax

NestJS

import { CacheModule } from '@nestjs/common';

@Module({
  imports: [
    CacheModule.register({
      ttl: 60, // seconds to keep cache
      max: 100, // max items in cache
    }),
  ],
})
export class AppModule {}

ttl means how long the cache stays before it clears automatically.

You can customize cache settings globally by passing options to register().

Examples

Cache items expire after 5 seconds.

NestJS

CacheModule.register({ ttl: 5 })

Cache keeps up to 100 items, each expires after 10 seconds.

NestJS

CacheModule.register({ ttl: 10, max: 100 })

Uses default cache settings (ttl: 60 seconds, max: 100 items).

NestJS

CacheModule.register()

Sample Program

This example sets up caching for the /count route. The first time you call it, it increases the counter. For 10 seconds, repeated calls return the cached count without increasing it.

NestJS

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

@Controller()
@UseInterceptors(CacheInterceptor)
export class AppController {
  private counter = 0;

  @Get('count')
  getCount() {
    this.counter++;
    return { count: this.counter };
  }
}

@Module({
  imports: [CacheModule.register({ ttl: 10 })],
  controllers: [AppController],
})
export class AppModule {}

Important Notes

CacheModule uses in-memory cache by default, which is good for simple apps or development.

For production, consider using external stores like Redis by using CacheModule.registerAsync() with custom store.

Remember to use @UseInterceptors(CacheInterceptor) on controllers or routes to enable caching behavior.

Summary

CacheModule helps speed up your app by storing data temporarily.

You set it up by importing and registering it with options like ttl.

Use cache interceptors to apply caching to routes easily.

Practice

1. What is the main purpose of importing CacheModule in a NestJS application?

easy

A. To enable temporary storage of data to speed up responses

B. To connect to a database automatically

C. To handle user authentication

D. To manage application logging

Solution

1. Step 1: Understand CacheModule's role

   CacheModule is used to store data temporarily to reduce repeated processing.

2. Step 2: Compare with other options

   It does not handle database, authentication, or logging directly.

3. Final Answer:

   To enable temporary storage of data to speed up responses -> Option A

4. Quick Check:

   CacheModule = temporary data storage [OK]

Hint: CacheModule is about caching data, not databases or auth [OK]

Common Mistakes:

• Confusing CacheModule with database modules
• Thinking CacheModule manages authentication
• Assuming CacheModule handles logging

2. Which of the following is the correct way to import and register CacheModule with a TTL of 5 seconds in a NestJS module?

easy

A. CacheModule.register({ ttl: 5 })

B. CacheModule.forRoot({ ttl: 5 })

C. CacheModule.setup({ ttl: 5 })

D. CacheModule.init({ ttl: 5 })

Solution

1. Step 1: Recall CacheModule registration method

   CacheModule uses the static method register to configure options like ttl.

2. Step 2: Verify method names

   Methods like forRoot, setup, or init are not used by CacheModule.

3. Final Answer:

   CacheModule.register({ ttl: 5 }) -> Option A

4. Quick Check:

   Use register() to configure CacheModule [OK]

Hint: CacheModule uses register(), not forRoot() or init() [OK]

Common Mistakes:

• Using forRoot() instead of register()
• Using setup() or init() which do not exist
• Forgetting to pass options inside register()

3. Given this NestJS module setup:

import { CacheModule, Module } from '@nestjs/common';

@Module({
  imports: [CacheModule.register({ ttl: 10 })],
})
export class AppModule {}

What will be the effect of the ttl: 10 option?

medium

A. Cache entries expire after 10 minutes

B. Cache entries expire after 10 seconds

C. Cache entries never expire

D. Cache entries expire immediately

Solution

1. Step 1: Understand ttl meaning in CacheModule

   The ttl option sets the time-to-live in seconds for cached data.

2. Step 2: Interpret ttl: 10

   Since ttl is 10, cached data expires after 10 seconds.

3. Final Answer:

   Cache entries expire after 10 seconds -> Option B

4. Quick Check:

   ttl = seconds cache lives [OK]

Hint: ttl value is in seconds, not minutes [OK]

Common Mistakes:

• Assuming ttl is in minutes
• Thinking ttl disables expiration
• Confusing ttl with cache size

4. Identify the error in this CacheModule setup:

import { CacheModule, Module } from '@nestjs/common';

@Module({
  imports: [CacheModule.register({ ttl: '20' })],
})
export class AppModule {}

medium

A. register() method does not accept options

B. CacheModule cannot be imported from '@nestjs/common'

C. ttl should be a number, not a string

D. Module decorator is missing parentheses

Solution

1. Step 1: Check ttl option type

   ttl expects a number representing seconds, not a string.

2. Step 2: Verify other parts

   CacheModule import and Module decorator usage are correct; register() accepts options.

3. Final Answer:

   ttl should be a number, not a string -> Option C

4. Quick Check:

   ttl must be numeric [OK]

Hint: ttl must be a number, not quoted text [OK]

Common Mistakes:

• Passing ttl as a string instead of number
• Thinking register() has no parameters
• Misusing import paths

5. You want to cache HTTP GET responses in a NestJS controller using CacheModule with a global TTL of 15 seconds. Which setup correctly applies caching to all routes in the module?

hard

A. Import CacheModule with ttl 15 and manually store cache in each method

B. Import CacheModule with ttl 15 and add @Cacheable() decorator on each method

C. Import CacheModule with ttl 15 and add @Cache() decorator on the module

D. Import CacheModule with ttl 15 and add @UseInterceptors(CacheInterceptor) on the controller

Solution

1. Step 1: Understand CacheModule and CacheInterceptor usage

   CacheModule provides caching, and CacheInterceptor applies caching behavior to routes.

2. Step 2: Apply CacheInterceptor globally on controller

   Using @UseInterceptors(CacheInterceptor) on the controller enables caching for all its routes.

3. Step 3: Evaluate other options

   No @Cacheable() or @Cache() decorators exist in NestJS core; manual caching is possible but not automatic.

4. Final Answer:

   Import CacheModule with ttl 15 and add @UseInterceptors(CacheInterceptor) on the controller -> Option D

5. Quick Check:

   Use CacheInterceptor with CacheModule for route caching [OK]

Hint: Use CacheInterceptor decorator to enable caching on controllers [OK]

Common Mistakes:

• Using non-existent decorators like @Cacheable or @Cache
• Not applying CacheInterceptor to controller or routes
• Trying manual caching instead of interceptor