Limitations of HTTP / 1.1 and some questions I had about it

I am exploring the backend fundamentals and networking these days, while I was exploring the stateless vs stateful protocols, I got to know something interesting that I want to share.
So I knew HTTP is built on top of TCP, I wondered how it all works, because HTTP is stateless and TCP is stateful. So I did some research and here’s how it all works.

HTTP / 1.1

The HTTP / 1.1 is built on top of TCP. In browsers, it has a limitation of 6 max connections. You might wonder if we can only have 6 open connections at max, how do I have multiple web apps and websites open in different tabs?

So the catch is it allows a maximum of 6 connections per domain. That’s what will enable you to use multiple websites in different tabs.

TCP

When we make a request to any website it first establishes a TCP connection with the server and then it sends the data via HTTP requests and response. These connections don’t are not long-living even though they are stateful. They persist for a short amount of time, based on the config you have on your server. It is called Keep Alive Timeout.

This Keep Alive Timeout is how long the connection stays alive after the server sends back a response.

Keep-Alive

By making use of this feature we can handle the Keep Alive Timeout per connection. This can be very useful if a particular API needs frequent access. So if we increase the Keep Alive time, the request will be handled faster because we don’t have to establish a connection again and go through the popular process of 3-way handshake again and again. This reduces our CPU and Memory usage on the server side because creating a new connection costs these resources.

It has some downsides, you can not keep connections open for too long it might slow down your server. So we have to be careful while doing this as an idle connection can block new requests

Below is an example in the Express server for it

const express = require('express');
const http = require('http');

const app = express();

app.get('/api/myblogs', (req, res) => {
    res.json({ message: "Here are your blogs!" });
});

// Create an HTTP server with optimized Keep-Alive settings
const server = http.createServer(app);

server.keepAliveTimeout = 60000; // 60 seconds
server.headersTimeout = 65000;  // Must be slightly higher than keepAliveTimeout

server.listen(3000, () => {
    console.log('Server running on port 3000');
});

Note: Reference actual networking documentation and books, I have just shared my learnings and understanding of it. If you feel I missed something or anything is wrong, post it in the comments.