Become an AWS pro by getting hands-on with API Gateway. Developed by AWS Solution Certified Architects, you’ll build secure apps, integrate services, and create a chat app. No setup, no cleanup, no hassle.

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API Gateway is an important component of the AWS serverless stack and has great potential to enable low latency, low-cost, and secure applications. This course takes you through all aspects of the AWS API Gateway and contains ready-to-use code snippets to implement different patterns of serverless API development in AWS. 

You’ll learn core concepts and get hands-on experience with core API Gateway capabilities. You’ll also dive deep into data mapping and WebSocket APIs and build a fully functional multi-user chat application with WebSocket API. You’ll learn about various services that can integrate with the API Gateway. Throughout the course, you’ll use IaC to provision resources, coupled with an introduction to CloudFormation. You’ll conclude the course by building a fully functional chat application with a bot that listens to the conversation and sends random jokes when asked.

Through detailed lessons covering theoretical and practical knowledge, this course helps you master the AWS API Gateway service.

AWS API Gateway: The Unsung Warrior

## What's WebSocket?
The REST API works on the HTTP protocol, which is unidirectional. The client sends a request to the server and gets a response. However, the server can’t go back to the client.

We need reverse communication in several business scenarios, like a chat application. When one user types the message, it must show on the other client. Therefore, the server can’t wait for the client to make an API call to fetch any pending notifications. Instead, the server must initiate it.

REST API can’t support this reverse communication, so WebSocket protocol was defined to handle it. The AWS API Gateway has an option to build a WebSocket API that leverages this WebSocket protocol to enable bidirectional communication between client and server.

## Connection ID
The intricacies of the protocol are beyond the scope of this course. On a high level, we can say that it works with a lasting connection between the client and server. We retain this connection even if there’s no data to transmit. Because the connection is always live, the client or the server can send a message whenever it’s available.

The API Gateway tracks this connection using a connection ID. Whenever a client invokes a WebSocket API, it creates a new connection and notes the connection ID. After this, any server-side code can invoke the API Gateway service to send a message to the client by using the connection identified by the connection ID.

We have another chapter dedicated to WebSocket connections, where we’ll dive deep to create a new chat application using the WebSocket API.

## Architecture pattern
A typical implementation of Websocket API in AWS is as follows:

# What's WebSocket?
The REST API works on the HTTP protocol, which is unidirectional. The client sends a request to the server and gets a response. However, the server can’t go back to the client.

We need reverse communication in several business scenarios, like a chat application. When one user types the message, it must show on the other client. Therefore, the server can’t wait for the client to make an API call to fetch any pending notifications. Instead, the server must initiate it.

REST API can’t support this reverse communication, so WebSocket protocol was defined to handle it. The AWS API Gateway has an option to build a WebSocket API that leverages this WebSocket protocol to enable bidirectional communication between client and server.

# Connection ID
The intricacies of the protocol are beyond the scope of this course. On a high level, we can say that it works with a lasting connection between the client and server. We retain this connection even if there’s no data to transmit. Because the connection is always live, the client or the server can send a message whenever it’s available.

The API Gateway tracks this connection using a connection ID. Whenever a client invokes a WebSocket API, it creates a new connection and notes the connection ID. After this, any server-side code can invoke the API Gateway service to send a message to the client by using the connection identified by the connection ID.

We have another chapter dedicated to WebSocket connections, where we’ll dive deep to create a new chat application using the WebSocket API.

# Architecture pattern
A typical implementation of Websocket API in AWS is as follows:

Understand the concept of WebSockets and the WebSocket API in the AWS API Gateway.

Introduction to API Gateway

API Gateway: High Level View

Getting Started with AWS API Gateway

API Gateway: Basic Configurations

Data Mapping Deep Dive

Leveraging AWS API Gateway for Public API Integration

Websocket Deep Dive

AWS Service Integration Deep Dive

Integrating AWS Services with API Gateway

Appendix

API Gateway Evaluation

Chat Application with Jokes Bot

Building a Chat Application Using Lambda Function and API Gateway

WebSocket API

What’s WebSocket?