EC2 introduces multiple changes to software development, deployment, and maintenance processes due to its flexibility, ease of deployment, instant scalability, and vast ecosystem of third-party services. However, EC2 functions differently from traditional on-premise servers, leading to novel performance issues that require different tools to gain visibility into an application and its underlying cloud-based infrastructure. The five most common performance issues in EC2 include unpredictable EBS disk I/O, EC2 instance ECU mismatch and stolen CPU, running out of EC2 instance memory, ELB load balancing traffic latency, and AWS maintenance and service interruptions. To detect these issues, one can use CloudWatch metrics such as VolumeQueueLength for EBS volumes, CPU Utilization for EC2 instances, Request Count for ELB, Healthy Host Count for ELB, and Latency for ELB. Problem avoidance and resolution strategies include selecting the right storage and instance types, adding swap volumes to EC2 instances, programming applications in a "server-disposable" manner, creating new ELB instances, and regularly checking the AWS account console and status page. Datadog can help with AWS EC2 performance issues by providing fast and easy graphing and alerting of EC2 performance metrics, automatic registration and categorization of new hosts, customizable alerting for AWS EC2, and slicing and dicing of performance metrics for analysis.