Application requirements have changed dramatically in recent years, requiring millisecond or even microsecond response times and 100 percent uptime. This change has led to a new wave of andquot;reactive applicationsandquot; with architectures that are event-driven, scalable, resilient, and responsive. In this session, we present the blueprint for building reactive applications on AWS. We compare reactive architecture to the classic n-tier architecture and discuss how it is cost-efficient and easy to implement using AWS. Next, we walk through how to design, build, deploy, and run reactive applications in the AWS cloud, delivering highly responsive user experiences with a real-time feel. This architecture uses Amazon EC2 instances to implement server push to broadcast events to application clients; AWS messaging (Amazon SQS/SNS); Amazon SWF to decouple system components; Amazon DynamoDB to minimize contention; and Elastic Load Balancing, Auto Scaling, Availability Zones, Amazon VPC, and Amazon Route 53 to make reactive applications scalable and resilient.