Amazon API Gateway FAQs

Amazon API Gateway is a fully managed service that makes it easy for developers to publish, maintain, monitor, and secure APIs at any scale. With a few clicks in the AWS Management Console, you can create an API that acts as a “front door” for applications to access data, business logic, or functionality from your back-end services, such as applications running on Amazon Elastic Compute Cloud (Amazon EC2), Amazon Elastic Container Service (Amazon ECS) or AWS Elastic Beanstalk, code running on AWS Lambda, or any web application. Amazon API Gateway handles all of the tasks involved in accepting and processing up to hundreds of thousands of concurrent API calls, including traffic management, authorization and access control, monitoring, and API version management. Amazon API Gateway has no minimum fees or startup costs. For HTTP APIs and REST APIs, you pay only for the API calls you receive and the amount of data transferred out. For WebSocket APIs, you pay only for messages sent and received and for the time a user/device is connected to the WebSocket API.

Amazon API Gateway provides developers with a simple, flexible, fully managed, pay-as-you-go service that handles all aspects of creating and operating robust APIs for application back ends. With API Gateway, you can launch new services faster and with reduced investment so you can focus on building your core business services. API Gateway was built to help you with several aspects of creating and managing APIs:

1) Metering. API Gateway helps you define plans that meter and restrict third-party developer access to your APIs. You can define a set of plans, configure throttling, and quota limits on a per API key basis. API Gateway automatically meters traffic to your APIs and lets you extract utilization data for each API key.

2) Security. API Gateway provides you with multiple tools to authorize access to your APIs and control service operation access. API Gateway allows you to leverage AWS administration and security tools, such as AWS Identity and Access Management (IAM) and Amazon Cognito, to authorize access to your APIs. API Gateway can verify signed API calls on your behalf using the same methodology AWS uses for its own APIs. Using custom authorizers written as AWS Lambda functions, API Gateway can also help you verify incoming bearer tokens, removing authorization concerns from your backend code.

3) Resiliency. API Gateway helps you manage traffic with throttling so that backend operations can withstand traffic spikes. API Gateway also helps you improve the performance of your APIs and the latency your end users experience by caching the output of API calls to avoid calling your backend every time.

4) Operations Monitoring. After an API is published and in use, API Gateway provides you with a metrics dashboard to monitor calls to your services. The API Gateway dashboard, through integration with Amazon CloudWatch, provides you with backend performance metrics covering API calls, latency data and error rates. You can enable detailed metrics for each method in your APIs and also receive error, access or debug logs in CloudWatch Logs.

5) Lifecycle Management. After an API has been published, you often need to build and test new versions that enhance or add new functionality. API Gateway lets you operate multiple API versions and multiple stages for each version simultaneously so that existing applications can continue to call previous versions after new API versions are published.

6) Designed for Developers. API Gateway allows you to quickly create APIs and assign static content for their responses to reduce cross-team development effort and time-to-market for your applications. Teams who depend on your APIs can begin development while you build your backend processes.

7) Real-Time Two-Way Communication. Build real-time two-way communication applications such as chat apps, streaming dashboards, and notifications without having to run or manage any servers. API Gateway maintains a persistent connection between connected users and enables message transfer between them.

Amazon API Gateway offers two options to create RESTful APIs, HTTP APIs and REST APIs, as well as an option to create WebSocket APIs.

HTTP API: HTTP APIs are optimized for building APIs that proxy to AWS Lambda functions or HTTP backends, making them ideal for serverless workloads. They do not currently offer API management functionality.

REST API: REST APIs offer API proxy functionality and API management features in a single solution. REST APIs offer API management features such as usage plans, API keys, publishing, and monetizing APIs.

WebSocket API: WebSocket APIs maintain a persistent connection between connected clients to enable real-time message communication. With WebSocket APIs in API Gateway, you can define backend integrations with AWS Lambda functions, Amazon Kinesis, or any HTTP endpoint to be invoked when messages are received from the connected clients.

To get started with HTTP APIs, you can use the Amazon API Gateway console, the AWS CLI, AWS SDKs, or AWS CloudFormation. To learn more about getting started with HTTP APIs, visit our documentation.

To get started with REST APIs, you can use the Amazon API Gateway console, the AWS CLI, or AWS SDKs. To learn more about getting started with REST APIs, visit our documentation.

You can build RESTful APIs using both HTTP APIs and REST APIs in Amazon API Gateway.

HTTP APIs are optimized for building APIs that proxy to AWS Lambda functions or HTTP backends, making them ideal for serverless workloads. HTTP APIs are a cheaper and faster alternative to REST APIs, but they do not currently support API management functionality. REST APIs are intended for APIs that require API proxy functionality and API management features in a single solution.

HTTP APIs are ideal for:

1. Building proxy APIs for AWS Lambda or any HTTP endpoint
2. Building modern APIs that are equipped with OIDC and OAuth 2 authorization 
3. Workloads that are likely to grow very large
4. APIs for latency sensitive workloads

1. Customers looking to pay a single price point for an all-inclusive set of features needed to build, manage, and publish their APIs. 

HTTP APIs come standard with CORS support, OIDC and OAuth2 support for authentication and authorization, and automatic deployments on stages.

Yes, you can import an API definition using OpenAPI 3. It will result in the creation of routes, integrations, and API models. For more information on importing OpenAPI definitions, see our documentation.

To migrate from your current REST API to a HTTP API in Amazon API Gateway, do the following:

1. Check that all the features you need are available in HTTP. To see the complete feature list, visit our documentation. 
2. Go to your REST API and export the OpenAPI definition from your REST API
3. Go to your HTTP API and import the OpenAPI definition from the previous step
4. Test the API functions as expected
5. Update your clients with the new URL

While your API might work, you may notice some missing features. To identify any missing features, review the Info, Warning, and Error fields from the Import operation. For more information about migrating REST APIs to HTTP APIs, see our documentation.

First, go to your REST and export the OpenAPI definition from your REST API. Then, go to your HTTP API and import the OpenAPI definition from the previous step. While your API might work, you may notice some missing features. To identify any missing features, review the Info, Warning, and Error fields from the Import operation. The AWS CLI will return information about your API within your info and warning fields. For more, read our documentation.

To get started, you can create a WebSocket API using the AWS Management Console, AWS CLI, or AWS SDKs. You can then set WebSocket routing to indicate the backend services such as AWS Lambda, Amazon Kinesis, or your HTTP endpoint to be invoked based on the message content. Refer to the documentation for getting started with WebSocket APIs in API Gateway.

Yes, all of the APIs created with Amazon API Gateway expose HTTPS endpoints only. Amazon API Gateway does not support unencrypted (HTTP) endpoints. By default, Amazon API Gateway assigns an internal domain to the API that automatically uses the Amazon API Gateway certificate. When configuring your APIs to run under a custom domain name, you can provide your own certificate for the domain.

APIs built on Amazon API Gateway can accept any payloads sent over HTTPS for HTTP APIs, REST APIs, and WebSocket APIs. Typical data formats include JSON, XML, query string parameters, and request headers. You can declare any content type for your APIs responses, and then use the transform templates to change the back-end response into your desired format.

Amazon API Gateway can execute AWS Lambda functions in your account, start AWS Step Functions state machines, or call HTTP endpoints hosted on AWS Elastic Beanstalk, Amazon EC2, and also non-AWS hosted HTTP based operations that are accessible via the public Internet.API Gateway also allows you to specify a mapping template to generate static content to be returned, helping you mock your APIs before the backend is ready. You can also integrate API Gateway with other AWS services directly – for example, you could expose an API method in API Gateway that sends data directly to Amazon Kinesis.

API Gateway generates custom SDKs for mobile app development with Android and iOS (Swift and Objective-C), and for web app development with JavaScript. API Gateway also supports generating SDKs for Ruby and Java. Once an API and its models are defined in API Gateway, you can use the AWS console or the API Gateway APIs to generate and download a client SDK. Client SDKs are only generated for REST APIs in Amazon API Gateway.

To see where HTTP APIs, REST APIs, WebSocket APIs are available, view the AWS region table here.

Through the Amazon API Gateway console, you can define the REST API and its associated resources and methods, manage the API lifecycle, generate client SDKs and view API metrics. You can also use the API Gateway console to define your APIs’ usage plans, manage developers’ API keys, and configure throttling and quota limits. All of the same actions are available through the API Gateway APIs.

A resource is a typed object that is part of your API’s domain. Each resource may have associated a data model, relationships to other resources, and can respond to different methods.You can also define resources as variables to intercept requests to multiple child resources.

Each resource within a REST API can support one or more of the standard HTTP methods. You define which verbs should be supported for each resource (GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS) and their implementation. For example, a GET to the cars resource should return a list of cars. To connect all methods within a resource to a single backend endpoint, API Gateway also supports a special “ANY” method.

Usage plans help you declare plans for third-party developers that restrict access only to certain APIs, define throttling and request quota limits, and associate them with API keys. You can also extract utilization data on a per-API key basis to analyze API usage and generate billing documents. For example, you can create a basic, professional, and enterprise plans – you can configure the basic usage plan to only allow 1,000 requests per day and a maximum of 5 requests per second (RPS).

With Amazon API Gateway, each REST API can have multiple stages. Stages are meant to help with the development lifecycle of an API -- for example, after you’ve built your APIs and you deploy them to a development stage, or when you are ready for production, you can deploy them to a production stage.

In Amazon API Gateway, stages are similar to tags. They define the path through which the deployment is accessible. For example, you can define a development stage and deploy your cars API to it. The resource will be accessible at https://www.myapi.com/dev/cars. You can also set up custom domain names to point directly to a stage, so that you don’t have to use the additional path parameter. For example, if you pointed myapi.com directly to the development stage, you could access your cars resource at https://www.myapi.com/cars. Stages can be configured using variables that can be accessed from your API configuration or mapping templates.

Stage variables let you define key/value pairs of configuration values associated with a stage. These values, similarly to environment variables, can be used in your API configuration. For example, you could define the HTTP endpoint for your method integration as a stage variable, and use the variable in your API configuration instead of hardcoding the endpoint – this allows you to use a different endpoint for each stage (e.g. dev, beta, prod) with the same API configuration. Stage variables are also accessible in the mapping templates and can be used to pass configuration parameters to your Lambda or HTTP backend.

A Resource Policy is a JSON policy document that you attach to an API to control whether a specified principal (typically an IAM user or role) can invoke the API. You can use a Resource Policy to enable users from a different AWS account to securely access your API or to allow the API to be invoked only from specified source IP address ranges or CIDR blocks. Resource Policies can be used with REST APIs in Amazon API Gateway.

Amazon API Gateway saves the history of your deployments. At any point, using the Amazon API Gateway APIs or the console, you can roll back a stage to a previous deployment.

Yes. You can use our open source Swagger importer tool to import your Swagger API definitions into Amazon API Gateway. With the Swagger importer tool you can create and deploy new APIs as well as update existing ones.

You can monetize your APIs on API Gateway by publishing them as products in AWS Marketplace. You will first need to register as a seller in AWS Marketplace, and submit your usage plans on API Gateway as products. Read here to learn more about API Monetization.

API Gateway offers the ability to create, update, and delete documentation associated with each portion of your API, such as methods and resources. You can access documentation-related APIs through the AWS SDKs, CLI, via RESTful calls, or by editing the documentation strings directly in the API Gateway console. Documentation can also be imported as a Swagger file, either as part of the API or separately, allowing you to add or update the documentation without disturbing the API definition. API Gateway conforms to the Open API specification for documentation imported from, or exported to, Swagger files. Documentation is supported for REST APIs in API Gateway.

In addition to offering standards-conformant API documentation support, API Gateway additionally supports documentation inheritance, making it simple to define a documentation string once and then use it in multiple places. Inheritance simplifies the process of defining API documentation, and can be converted to the standard representation when exporting the API as a Swagger file.

Yes, you can apply a Resource Policy to an API to restrict access to a specific Amazon VPC or VPC endpoint. You can also give an Amazon VPC or VPC endpoint from a different account access to the Private API using a Resource Policy.