A Network Load Balancer (NLB) is a Layer 4 load balancer designed for extreme performance, capable of handling millions of requests per second with ultra-low latencies and preserving the client's source IP address by default [citation:1][citation:6].
A Network Load Balancer (NLB) operates at the connection level (Layer 4 of the OSI model). It is designed to handle millions of requests per second while maintaining ultra-low latencies, making it ideal for TCP, UDP, and TLS traffic. The NLB is optimized for sudden, volatile traffic patterns and provides a static IP address per Availability Zone. By default, it preserves the client-side source IP address, allowing your backend instances to see the original IP of the client [citation:1][citation:6].