---
title: "Scaling Websites for Millions of Users"
description: "Learn how to scale your website architecture to support millions of users."
image: "https://assets.bytebytego.com/diagrams/0322-scale-to-million.jpg"
createdAt: "2024-02-07"
draft: false
categories:
  - cloud-distributed-systems
tags:
  - scalability
  - architecture
---

![](https://assets.bytebytego.com/diagrams/0322-scale-to-million.jpg)

The diagram below illustrates the evolution of a simplified eCommerce website. It goes from a monolithic design on one single server, to a service-oriented/microservice architecture.

Suppose we have two services: inventory service (handles product descriptions and inventory management) and user service (handles user information, registration, login, etc.).

## Step 1

With the growth of the user base, one single application server cannot handle the traffic anymore. We put the application server and the database server into two separate servers.

## Step 2

The business continues to grow, and a single application server is no longer enough. So we deploy a cluster of application servers.

## Step 3

Now the incoming requests have to be routed to multiple application servers, how can we ensure each application server gets an even load? The load balancer handles this nicely.

## Step 4

With the business continuing to grow, the database might become the bottleneck. To mitigate this, we separate reads and writes in a way that frequent read queries go to read replicas. With this setup, the throughput for the database writes can be greatly increased.

## Step 5

Suppose the business continues to grow. One single database cannot handle the load on both the inventory table and user table. We have a few options:

*   **Vertical partition.** Adding more power (CPU, RAM, etc.) to the database server. It has a hard limit.
*   **Horizontal partition** by adding more database servers.
*   Adding a caching layer to offload read requests.

## Step 6

Now we can modularize the functions into different services. The architecture becomes service-oriented / microservice.