Amazon API Gateway is a managed service to enable you to publish and manage APIs.  You can then enable your applications to access data, business logic, and functionality from your back end services which can include applications running on EC2 Instances or Lambda functions.   The API Gateway itself will accept incoming API calls and forward them to the backend services and thus manages all tasks involved in processing thousands of concurrent API calls.  This article, Amazon API Gateway Exam Tips gives you an overview of the core concepts you need to remember for the AWS Certified Solutions Architect Associate Exam.

Amazon API Gateway has no minimum fees or start-up costs. You pay only for the API calls you receive and the amount of data transferred out.

API Caching

You can configure your API Gateway with a cache and time to live (TTL) so that you do not have to forward all requests to your end points.  When the cache is enabled, the API Gateway can respond with the data held in cache.  This also means that you improve latency as well as avoid excessive requests being made to your end points.

Key Points to Note:

  • Cache settings enable you to control how the cache key is built
  • You need to specify the time-to-live (TTL)
  • You need to specify the size of the cache in gigabytes

Throttle Requests to your API Gateway

Amazon API Gateway automatically protects your backend systems from distributed denial-of-service (DDoS) attacks. However, you can also manage traffic to your back-end systems by setting throttling rules, based on the number of requests per second, for each HTTP method in your APIs.

You set your throttling limits for standard rates and bursts. As an example, you can set a rate limit of 2,000 requests per second for a specific method in their REST APIs, and then configure the Gateway to handle a burst of 3,000 requests per second for a few seconds. Amazon API Gateway will track the number of requests per second and if it goes over the limit, you will receive a 429 HTTP response. Throttling ensures that API traffic is controlled to help your backend services maintain performance and availability.

Integration with CloudWatch

Amazon API Gateway sends logging information and metrics to Amazon CloudWatch which can then be used to setup custom alarms. Amazon API Gateway integrates with Amazon CloudWatch Logs and you can enable logging for each stage in your API. For each method in your REST APIs, you can set the verbosity of the logging, and if the full request and response data should be logged.

Logs, alarms, error rates and other metrics are stored in Amazon CloudWatch and are available near real time. Finally, Amazon API Gateway is integrated with AWS CloudTrail to give you a full auditable history of the changes to your REST APIs.

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