How to Build a Scalable Application up to 1 Million Users on AWS

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Suppose you’ve built a web application and started getting few customers. After some feedback and suggestions, you are ready with a full-fledged product. Now, your marketing team shares your app on product hunt to acquire new customers. Suddenly, thousands of visitors are using your app and at one point they are unable to use your app.

You’ve tested your app and it is working fine. So what happened?

“This is not a bug but a problem of scalability. Your cloud architecture is not designed to scale with increasing load.”

I’ve seen many companies that usually focus more on features and less on scalability. Creating applications that are both resilient and scalable is an essential part of any application architecture. In this blog, you will learn how to build highly scalable web application architecture that can scale with increasing load.

Scalability refers to the ability of a system to give a reasonable performance under growing demands (This can be larger data-sets, higher request rates, the combination of size and velocity, etc). It should work well with 1 user or 1 million users and handles spikes in traffic automatically. By adding and removing the resources only when needed, scalable apps consume only the resources necessary to meet demand.

When talking about scalability in cloud computing, you will often hear about two main ways of scaling — horizontal or vertical. Let’s look deeper into these terms.

Vertical scaling (Scaling Up)

Scaling up or vertical scaling refers to the resource maximization of a single unit to expand its ability to handle the increasing load. In hardware terms, this includes adding processing power and memory to the physical machine running the server. In software terms, scaling up may include optimizing algorithms and application code.

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Horizontal scaling (Scaling Out)

Scaling out or horizontal scaling refers to resource increment by the addition of units to the app’s cloud architecture. This means adding more units of smaller capacity instead of adding a single unit of larger capacity. The requests for resources are then spread across multiple units thus reducing the excess load on a single machine.

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What does scalability look like? There are some areas where an app needs to excel to be considered scalable.


First and foremost, the application must operate well under stress with low latency. The speed of a website affects usage and user satisfaction, as well as search engine rankings, a factor that directly correlates to revenue and retention. As a result, creating a scalable web application architecture that is optimized for fast responses and low latency is key.

Availability and Reliability

These are closely related and equally necessary. Scalable apps rarely if ever go down under stress. They need to reliably produce data upon request and not lose stored information.


The manageability of the cloud architecture equates to the scalability of operations: maintenance and updates. Things to consider for manageability are the ease of diagnosing and understanding problems when they occur, ease of making updates or modifications, and how simple the system is to operate. (i.e., does it routinely operate without failure or exceptions?)


Highly scalable applications don’t have to be unreasonably expensive to build, maintain, or scale. Planning for scalability during development allows the app to expand as demand increases without causing undue expenses.

You’ve plenty of options to choose the cloud provider while building the high-performance web application architecture. The three leading cloud computing vendors, AWS, Microsoft Azure, and Google Cloud, each have their own strengths and weaknesses that make them ideal for different use cases.

In this blog, I’ve chosen AWS to show you how to build a web scalable application. AWS is a subsidiary of the renowned company, Amazon, it provides different services that are cloud-centered for various requirements. AWS holds the highest 33% market share of cloud computing. They provide excellent documentation on each of their services, helpful guides and white papers, reference architectures for common apps.

Steps to build a scalable application based on increasing users from 1 to 1 million

Initial Setup of Cloud Architecture

Create multiple hosts and choose the database

Store database on Amazon RDS

Create multiple availability zones

Move static content to object-based storage

Auto Scaling

Service-Oriented Architecture(SOA)

Claritus, a global mobile and web application development services company with 250+ app developers to design apps.

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