Load Balancing L4/L7 in Go — DSR, Rate Limiting & API Gateway
Prerequisite: Part 2 of the System Design Masterclass. Read Part 1: System Design Thinking first to understand foundational trade-off frameworks. Answer-first: L4 load balancing routes traffic by transport-layer (IP/TCP/UDP) metadata — minimal CPU overhead but limited intelligence. L7 load balancing inspects HTTP headers, paths, and cookies — enables content-based routing and advanced health checks at the cost of higher processing overhead per request. L4 vs L7 Load Balancing — The Definitive Comparison Answer-first: The fundamental difference is where in the network stack the routing decision is made. L4 (Transport Layer) routes at TCP/UDP level using IP+port tuples. L7 (Application Layer) routes at HTTP level using headers, URLs, and payloads. ...