When an HTTP POST request is made to the API Gateway endpoint, API Gateway authorizes the request by checking Basic auth credentials for valid credentials. To do this, API Gateway calls a Lambda authorizer function that validates the request and returns whether the request is valid or not.

When the request is accepted, API Gateway forwards the message payload to an SQS queue.

A new message in the queue triggers a Lambda function. The function consumes events from the queue and inserts the payload into an Amazon DynamoDB table.

If there is any problem processing the message in the function, SQS has a DLQ (dead letter queue) configured, to which problematic messages are sent.