Limit payload size using a reverse-proxy or a middleware

One Paragraph Explainer

Parsing request bodies, for example JSON-encoded payloads, is a performance-heavy operation, especially with larger requests. When handling incoming requests in your web application, you should limit the size of their respective payloads. Incoming requests with unlimited body/payload sizes can lead to your application performing badly or crashing due to a denial-of-service outage or other unwanted side-effects. Many popular middleware-solutions for parsing request bodies, such as the already-included body-parser package for express, expose options to limit the sizes of request payloads, making it easy for developers to implement this functionality. You can also integrate a request body size limit in your reverse-proxy/web server software if supported. Below are examples for limiting request sizes using express and/or nginx.

Example code for express

const express = require('express');
const app = express();
app.use(express.json({ limit: '300kb' })); // body-parser defaults to a body size limit of 100kb
// Request with json body
app.post('/json', (req, res) => {
    // Check if request payload content-type matches json, because body-parser does not check for content types
    if (!req.is('json')) {
        return res.sendStatus(415); // -> Unsupported media type if request doesn't have JSON body
    }
    res.send('Hooray, it worked!');
});
app.listen(3000, () => console.log('Example app listening on port 3000!'));

Express docs for express.json()

Example configuration for nginx

http {
    ...
    # Limit the body size for ALL incoming requests to 1 MB
    client_max_body_size 1m;
}
server {
    ...
    # Limit the body size for incoming requests to this specific server block to 1 MB
    client_max_body_size 1m;
}
location /upload {
    ...
    # Limit the body size for incoming requests to this route to 1 MB
    client_max_body_size 1m;
}

Nginx docs for client_max_body_size