L4 vs L7 Load Balancing#

The distinction between Layer 4 and Layer 7 load balancing determines what the load balancer can see and what routing decisions it can make.

Layer 4 (Transport) load balancers work at the TCP/UDP level. They see source/destination IPs and ports but not the content of the traffic. They forward raw TCP connections to backends. This makes them fast (no protocol parsing), protocol-agnostic (works for HTTP, gRPC, database connections, custom protocols), and transparent (the backend sees the original packets, mostly). Use L4 for database connections, raw TCP services, and when you need maximum throughput with minimum latency.