Resource Management and Scaling

Vertical scaling (scaling up) means increasing the power of an existing instance — more CPU, RAM, or storage. Horizontal scaling (scaling out) means adding more instances to distribute the load. AWS favors horizontal scaling because it provides better fault tolerance and no single point of failure. Auto Scaling groups handle horizontal scaling automatically based on demand.

Auto Scaling automatically adjusts the number of EC2 instances based on demand. You define minimum, maximum, and desired capacity. Scaling policies can be based on metrics like CPU utilization. When demand increases, Auto Scaling launches new instances; when demand drops, it terminates them. This ensures you have enough capacity without overpaying during low-demand periods.

ELB automatically distributes incoming traffic across multiple targets (EC2 instances, containers, IPs) in one or more AZs. Three types: Application Load Balancer (HTTP/HTTPS, Layer 7), Network Load Balancer (TCP/UDP, Layer 4, ultra-low latency), and Gateway Load Balancer (third-party virtual appliances). ELB improves availability by routing around unhealthy targets.

Amazon Elastic Compute Cloud (EC2) provides resizable virtual servers (instances) in the cloud. You choose the instance type (CPU, memory, storage, networking), operating system, and software. EC2 offers multiple purchasing options: On-Demand (pay per hour/second), Reserved Instances (1 or 3-year commitment for discount), Spot Instances (unused capacity at up to 90% discount), and Savings Plans.