Introduction to Caching requests with Redis in Node.js

What is Redis?

Redis is an remote dictionary server, an open-source (BSD licensed), in-memory data structure store, used as a database, cache, and message broker.

What is Caching?

Caching is the process of storing data into a software or hardware component so that future requests for that data can be served faster.

Install Redis on your machine

sudo apt update

sudo apt install redis-server

sudo systemctl status redis

Create a new Directory & generate package.json file

npm init

we will use the following npm package in this project:

Express - for routing.

Node fetch - To make http request.

Redis - as node.js redis client.

nodemon  - to setup &  restart the server

Now that you have redis installed, add the following code to the index.js file.

var express = require('express')
var fetch = require("node-fetch");
var redis = require('redis')
 
var app = express()
 

var client = redis.createClient(6859)
 
client.on('error', (err) => {
    console.log("Error " + err)
});
 
// get the list of photos
app.get('/photos', (req, res) => {
 
    var photosRedisKey = 'user:photos';
 
    // Firstly fetch the data from Redis in case we have it cached in redis
    return client.get(photosRedisKey, (err, photos) => {
 
        // If that data exists in Redis
        if (photos) {
 
            return res.json({ source: 'cache', data: JSON.parse(photos) })
 
        } else { 
 
            // Now Fetch data directly from remote server api
            fetch('https://jsonplaceholder.typicode.com/photos')
                .then(response => response.json())
                .then(photos => {
 
                    // Now Save the API response in Redis store,  api server data automatically expire in 3600 seconds
                    client.setex(photosRedisKey, 3600, JSON.stringify(photos))
 
                    // Send JSON response to client browser
                    return res.json({ source: 'api', data: photos })
 
                })
                .catch(error => {
                    // log error message
                    console.log(error)
                    return res.json(error.toString())
                })
        }
    });
});
 
// Assign express port at 3000 
app.listen(3000, () => {
    console.log('Server listening on port: ', 3000)
});

Goto postman and hit URL http://localhost:3000/photos and see the response time:

First Request : 

Second Request:

The first request took 41ms and the second request took 30ms.

Conclusion

Redis is a very powerful in-memory data-store tool that we can use in our applications to cache data for upcoming requests. It's very simple to save and get data without much overhead.