This chapter of our Python with Lambda and API Gateway for backend development course will introduce the development of GraphQL APIs with API Gateway and Lambda, with a special focus on authentication and authorization in GraphQL APIs.
GraphQL is an open data query language that allows customers to request exactly the data they need. This makes it easier to evolve APIs over time and allows developers to create more powerful APIs. AWS offers AWS AppSync, a service that makes it easy to develop scalable and secure GraphQL APIs on AWS, but in this chapter, we'll focus on how you can build your own GraphQL APIs using API Gateway and Lambda.
To create a GraphQL API with API Gateway and Lambda, you need to define a GraphQL schema and create Lambda functions that resolve the various operations defined in your schema. API Gateway acts as an HTTP entry point for your Lambda functions, allowing you to expose them as API endpoints.
Once your GraphQL API is up and running, the next step is to implement authentication and authorization. Authentication refers to the process of verifying a user's identity, while authorization refers to the process of verifying what an authenticated user is allowed to do.
There are several strategies for implementing authentication and authorization in GraphQL APIs. A common approach is to use JWT tokens (JSON Web Tokens) for authentication and role-based rules for authorization. JWT tokens are generated when a user authenticates and include information about the user's identity. Lambda functions can then check the validity of these tokens and use the information in them to determine whether a user has permission to perform a certain operation.
To implement this approach, you will need to configure an authentication service that can generate JWT tokens. There are many authentication services available, including AWS Cognito, which integrates well with API Gateway and Lambda. Once you've configured your authentication service, you can configure API Gateway to verify JWT tokens on all incoming requests. This can be done using a custom authorizer, which is a Lambda function that API Gateway calls before forwarding a request to your other Lambda functions.
After API Gateway verifies authentication, your Lambda functions can then handle authorization. To do this, they need to check the claims on the JWT token and determine whether the user has permission to perform the requested operation. This is often done using role-based rules, where different roles are allowed to perform different operations.
For example, you might have an "admin" role that is allowed to perform any operations and a "user" role that is only allowed to perform operations on its own data. Authorization rules can be coded directly into your Lambda functions, or you can use a service like AWS IAM to manage your authorization rules.
In summary, developing GraphQL APIs with API Gateway and Lambda offers a powerful and flexible way to create backend APIs. Authentication and authorization are critical components of any API, and API Gateway and Lambda offer several options for implementing them. With the right strategy, you can create secure, scalable GraphQL APIs that meet your users' needs.
In the next chapter, we will delve into how to implement queries and mutations in GraphQL APIs with API Gateway and Lambda. Stay tuned!
