Now consider the following diagram:

In general, it's important to monitor systems for any suspicious activity, or even spot any performance issues with systems. API Gateway, DynamoDB, and Lambda functions all have built-in support for CloudWatch and X-Ray for that specific task. CloudWatch allows you to track metrics and monitor log files, set specific alarms, and automatically react to changes in your AWS resources. X-Ray is a service that traces requests and can also generate specific service maps. The combination of these free systems gives you very good insight, an out-of-the-box view, into how your serverless system is performing. CloudTrail is another service that allows you to monitor all APIs and access to resources by any user or system.