Custom cache keys in NestJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the CacheInterceptor from NestJS.

NestJS

import { [1] } from '@nestjs/common';

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ACacheInterceptor

BCacheModule

CCacheService

DCacheKey

Attempts:

3 left

💡 Hint

Common Mistakes

Importing CacheModule instead of CacheInterceptor

Using CacheService which is not a valid import here

The CacheInterceptor is imported from @nestjs/common to enable caching features.

2fill in blank

medium

Complete the code to create a custom cache key by overriding the trackBy method.

NestJS

export class CustomCacheInterceptor extends CacheInterceptor {
  protected trackBy(context: ExecutionContext): string | undefined {
    const request = context.switchToHttp().getRequest();
    return request.method + ':' + [1];
  }
}

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Arequest.headers

Brequest.body

Crequest.params

Drequest.url

Attempts:

3 left

💡 Hint

Common Mistakes

Using request.body which may vary and cause cache misses

Using request.headers which is not a stable cache key

The cache key is often based on the HTTP method and the request URL to uniquely identify requests.

3fill in blank

hard

Fix the error in the custom cache key function to correctly handle query parameters.

NestJS

protected trackBy(context: ExecutionContext): string | undefined {
  const request = context.switchToHttp().getRequest();
  const key = request.method + ':' + request.url + '?' + [1];
  return key;
}

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Arequest.params

Brequest.query

Crequest.body

Drequest.headers

Attempts:

3 left

💡 Hint

Common Mistakes

Using request.params which holds route parameters, not query parameters

Using request.body which is for POST data

Query parameters are accessed via request.query to include them in the cache key.

4fill in blank

hard

Fill both blanks to create a cache key that includes method, URL, and a user ID from headers.

NestJS

protected trackBy(context: ExecutionContext): string | undefined {
  const request = context.switchToHttp().getRequest();
  const userId = request.headers['[1]'];
  return request.method + ':' + request.url + ':' + [2];
}

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Ax-user-id

Bauthorization

CuserId

Duser-agent

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'authorization' header which contains tokens, not user ID

Using 'user-agent' which is unrelated to user identity

The user ID is often sent in a custom header like x-user-id. We retrieve it and include it in the cache key.

5fill in blank

hard

Fill all three blanks to define a custom cache interceptor class with a trackBy method that uses method, URL, and a query param 'lang'.

NestJS

import { CacheInterceptor, ExecutionContext } from '@nestjs/common';

export class CustomCacheInterceptor extends [1] {
  protected trackBy(context: [2]): string | undefined {
    const request = context.switchToHttp().getRequest();
    const lang = request.query['[3]'];
    return request.method + ':' + request.url + ':' + lang;
  }
}

Drag options to blanks, or click blank then click option'

ACacheInterceptor

BExecutionContext

Clang

DCacheService

Attempts:

3 left

💡 Hint

Common Mistakes

Using CacheService instead of CacheInterceptor as base class

Using wrong type for context parameter

Using incorrect query parameter key

The class extends CacheInterceptor, the method argument is of type ExecutionContext, and the query parameter key is 'lang'.