Elastic Load Balancing (ELB) distributes incoming traffic across multiple targets (EC2 instances, containers, etc.) — improving availability (no single point of failure) and scalability (spread load). It's a key component for reliable, scalable applications.
What a load balancer does
A LOAD BALANCER sits in front of multiple backend targets and distributes requests:
Client → LOAD BALANCER → ┬→ Instance 1
├→ Instance 2
└→ Instance 3
→ spreads traffic across targets (scalability + no single instance overloaded)
→ HEALTH CHECKS: routes only to HEALTHY targets (an unhealthy one is bypassed)
→ if a target fails, traffic goes to the others → HIGH AVAILABILITY
→ single entry point (clients hit the LB, not individual instances)
