Building a Scalable WebSocket Server with AWS API Gateway

Are you looking to create a WebSocket server that can handle millions of simultaneous connections? In this article, we’ll explore how to build a highly scalable WebSocket server using AWS API Gateway and a serverless architecture. By leveraging the power of AWS services like API Gateway, Lambda, and DynamoDB, we can create a robust and efficient WebSocket server. Let’s dive in!

WebSocket: The Solution to Bidirectional Communication

Before WebSockets, developers relied on techniques like long polling and short polling to achieve bidirectional communication between clients and servers. However, these approaches were resource-intensive and had their limitations. WebSocket was introduced to address these issues and enable efficient bidirectional communication between clients and servers over a single TCP connection. Today, WebSockets are widely used in chat apps, games, and other real-time applications.

Getting Started with AWS and Serverless Framework

To begin our project, we’ll need to set up our AWS credentials and configure the Serverless Framework to interact with AWS. Once that’s done, we can install the Serverless Framework and get our project up and running.

Starting the Project

To start a new Serverless (SLS) project, simply use the command “sls” or “serverless” in your terminal. The prompt command will guide you through the project creation process. Check out the article for a visual example of how to configure your SLS project.

Serverless.yml File

The serverless.yml file contains all the project configurations, including runtime, environment variables, lambda function definitions, and required resources. This file allows us to define specific AWS roles for each function and package our files in a way that optimizes the package size and lambda start time.

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AWS API Gateway WebSocket APIs

AWS API Gateway provides WebSocket APIs, which allow for the integration of WebSocket routes with backend HTTP endpoints, Lambda functions, or other AWS services. By defining custom routes and leveraging predefined routes like $connect, $disconnect, and $default, we can create a powerful WebSocket API. The article provides a detailed explanation of routing and message handling.

Coding Our Functions

We’ll be creating three functions: $connect, $disconnect, and onMessage. The $connect function stores the connection ID in a DynamoDB table, while the onMessage function receives and rebroadcasts messages to all connected clients. The $disconnect function removes the connection ID from the DynamoDB table. The article includes sample code for each function along with explanations.

Deployment and Testing

To deploy our functions to AWS, we can simply run “sls deploy” in our terminal. The Serverless Framework will publish our services in the specified region and stage. After deployment, we can test our WebSocket server using tools like wscat to send and receive messages.


With the help of the Serverless Framework, we can easily develop and publish a fully serverless WebSocket server using AWS API Gateway. By leveraging AWS services like API Gateway, Lambda, and DynamoDB, we can create a highly scalable WebSocket server that can handle millions of simultaneous connections. This serverless architecture eliminates the need for provisioning and scaling resources, allowing developers to focus on building their applications. To learn more about the code and access the source code of this project, visit the ProgramMatek website.

So why wait? Start building your own scalable WebSocket server today with ProgramMatek!

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