Why caching reduces response latency in NestJS - See It in Action

Why caching reduces response latency

📖 Scenario: You are building a simple NestJS service that fetches user data. To make the service faster, you want to add caching so repeated requests for the same user do not take long.

🎯 Goal: Build a NestJS service that caches user data in memory to reduce response latency on repeated requests.

📋 What You'll Learn

Create a simple user data object

Add a cache variable to store fetched users

Implement a method to check cache before fetching user data

Return cached data if available, otherwise fetch and cache it

💡 Why This Matters

🌍 Real World

Caching is used in web services to speed up responses by storing data temporarily so repeated requests are faster.

💼 Career

Understanding caching helps backend developers optimize APIs and improve user experience by reducing wait times.

1

Create initial user data object

Create a constant called users that is an object with these exact entries: 1: { id: 1, name: 'Alice' }, 2: { id: 2, name: 'Bob' }, 3: { id: 3, name: 'Charlie' }.

NestJS

// Create the users object with three users
// Your code here

Need a hint?

Use a constant object named users with keys 1, 2, and 3 each holding an object with id and name.

2

Add cache storage variable

Add a variable called cache and set it to an empty object {} to store cached user data.

NestJS

const users = {
  1: { id: 1, name: 'Alice' },
  2: { id: 2, name: 'Bob' },
  3: { id: 3, name: 'Charlie' }
};

// Create cache object to store fetched users
// Your code here

Need a hint?

Use const cache = {} to create an empty object for caching.

3

Implement caching logic in getUser function

Write a function called getUser that takes id as a parameter. Inside, first check if cache[id] exists. If yes, return cache[id]. Otherwise, get the user from users[id], store it in cache[id], then return it.

NestJS

const users = {
  1: { id: 1, name: 'Alice' },
  2: { id: 2, name: 'Bob' },
  3: { id: 3, name: 'Charlie' }
};

const cache = {};

// Create getUser function with caching logic
// Your code here

Need a hint?

Use an if statement to check cache[id]. Return cached data if found. Otherwise, get from users, cache it, then return.

4

Export getUser function for use in NestJS service

Add export before the function getUser declaration to make it available outside this module.

NestJS

const users = {
  1: { id: 1, name: 'Alice' },
  2: { id: 2, name: 'Bob' },
  3: { id: 3, name: 'Charlie' }
};

const cache = {};

// Export getUser function
// Your code here

Need a hint?

Add export before the function to share it with other files.