Load balancer that works at the transport layer, routing traffic based only on IP address and port number without looking at the content. Like a mail sorter who only reads the address on the envelope, not what's inside.
A Layer 4 load balancer routes all traffic on port 443 to backend servers based on IP, handling millions of connections per second with very low latency.
All of these provide Layer 4 (TCP/UDP) load balancing that routes traffic using IP/port (and connection metadata) without inspecting HTTP content. They’re commonly used for high-throughput, low-latency, pass-through load balancing and non-HTTP protocols.