| Type | Layer | When |
|---|---|---|
| ALB (Application Load Balancer) | 7 | HTTP/HTTPS, hostname/path routing, WebSocket, gRPC |
| NLB (Network Load Balancer) | 4 | Ultra-low latency, static IPs, TCP/UDP, millions of requests/sec |
| CLB (Classic Load Balancer) | 4 + 7 | Legacy, avoid for new deployments |
| GWLB (Gateway Load Balancer) | 3 | Firewall/security appliance insertion |
ALB does: hostname routing, path routing, header routing, query string routing, WebSocket, sticky sessions, TLS termination, OIDC authentication.