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Triggers are pieces of code that will automatically respond to any events in DynamoDB Streams. DynamoDB is an AWS product just like Lambda, and therefore you’re able to create triggers with ease. Trigger functions can perform any actions you specify, like sending notifications or a workflow initiation. API Gateways, S3, and DynamoDB table streams are the 3 most common ways to trigger Lambda functions. API Gateway is one way to trigger a Lambda function, but this is generally seen as bad practice.