A. Use AWS Auto Scaling to scale up internal services when there is a surge in traffic.
B. Use different Availability Zones to host internal services. Send a notification to a system administrator when an internal service becomes unresponsive.
C. Use an Elastic Load Balancer to distribute the traffic between internal services. Configure Amazon CloudWatch metrics to monitor traffic to internal services.
D. Use Amazon Simple Queue Service (Amazon SQS) to store user requests as they arrive. Change the internal services to retrieve the requests from the queue for processing.