Day 13: AWS Compute Core — EC2, ELB, and Auto Scaling

Day 13 of the AWS Compute Core series focuses on the foundational services of EC2, Elastic Load Balancer, and Auto Scaling. Amazon EC2 provides virtual servers, or instances, where users have full control over the operating system, software, and hardware. The EC2 model falls under the Infrastructure as a Service (IaaS) category, giving customers complete responsibility for managing the server environment.

Key components of EC2 include AMIs (Amazon Machine Images), which are templates pre-configured with an operating system and software; instance types that define CPU, memory, and network capabilities; key pairs for secure access; and security groups that function as virtual firewalls controlling traffic.

Elasticity in AWS is the ability to automatically adjust the number of EC2 instances based on traffic demand, utilizing Auto Scaling. Horizontal scaling involves adding or removing instances to handle varying loads, while vertical scaling adjusts the size of a single instance. Elasticity is a short-term solution, unlike scalability, which involves modifying a single instance's resources to better accommodate workload demands.

High availability in AWS relies on redundancy, ensuring multiple servers run the application to eliminate single points of failure; monitoring, using ELB health checks to assess server health; and failover, which automatically reroutes traffic to healthy servers if an instance fails. These mechanisms work together to ensure uninterrupted service.

Elastic Load Balancer (ELB) acts as a traffic manager, distributing incoming requests across multiple EC2 instances across different Availability Zones. ELB, a managed service, eliminates the need for users to set up and maintain their own load balancing infrastructure, offering features like content-based routing with Application Load Balancers (ALB) and high-performance TCP/UDP support via Network Load Balancers (NLB). In generic discussion, ELB typically refers to ALB.