invocationType

The invocation type of the Amazon Web Services Lambda function. An invocation type of RequestResponse means that the execution of the function immediately results in a response, and a value of Event means that the function is invoked asynchronously. The default value is Event. For information about Amazon Web Services Lambda invocation types, see the Amazon Web Services Lambda Developer Guide.

There is a 30-second timeout on RequestResponse invocations. You should use Event invocation in most cases. Use RequestResponse only to make a mail flow decision, such as whether to stop the receipt rule or the receipt rule set.