AWS Elastic Load Balancing

AWS Elastic Load Balancing distributes incoming traffic across multiple targets so one failing instance does not take the whole application offline. For DevOps teams, it matters because it lets teams add or replace capacity behind a stable endpoint while still protecting users from unhealthy instances. Instead of relying on one fragile manual configuration, you can design a repeatable service boundary that stays stable while the workload behind it changes.

Core ideas

The main ideas to understand are Application Load Balancer works at layer 7 and understands HTTP and HTTPS requests; Network Load Balancer works at layer 4 for TCP and UDP traffic and is built for very high performance; Classic Load Balancer is the legacy option that still appears in older environments but lacks the flexibility of newer services; and target groups, health checks, and listener rules decide where requests go and when a target should be removed from rotation. These details shape architecture decisions, but they also shape day-to-day operations. When a team chooses defaults without understanding how the service behaves under failure, scale, or security review, the platform often becomes harder to debug than the application itself.

From an operations perspective, the goal is to pick the correct balancer type, register the right targets, and make health checks reflect real application readiness rather than a port-only probe. The comparison below highlights the choices that usually matter first. It is often better to start with a simpler design and add sophistication only after metrics, incidents, or delivery requirements prove the change is necessary.

Practical commands

aws elbv2 describe-load-balancers --query 'LoadBalancers[].{Name:LoadBalancerName,Type:Type,DNS:DNSName}' --output table
aws elbv2 describe-target-groups --query 'TargetGroups[].{Name:TargetGroupName,Protocol:Protocol,Port:Port}' --output table
aws elbv2 describe-target-health --target-group-arn arn:aws:elasticloadbalancing:REGION:ACCOUNT:targetgroup/app-tg/1234567890abcdef

Practical CLI checks make the service easier to support in real environments. Use the commands below to inspect the current state and confirm that automation matches intent. Before you promote a change, verify listener ports, target group health states, and deregistration behaviour before shifting production traffic. A safe default is graceful draining and application-level health checks that prove the dependency chain is usable. That discipline makes later troubleshooting, scaling, and security reviews far less painful.