Round Robin Is Lying to You: Equal Traffic Equal Load
> Your load balancer can distribute traffic perfectly and still overload a server. Here's the part of Round Robin we often overlook. Three servers. Six requests. Request 1 → Server A Request 2 → Server B Request 3 → Server C Request 4 → Server A Request 5 → Server B Request 6 → Server C Perfect. Every server got exactly two requests. So the load is balanced... right? Not necessarily. This is where a simple load-balancing diagram can hide a surprisingly important production problem: Equal traffic does not mean equal work. The Problem Isn't the Algorithm Round Robin is beautifully simple. You have three servers: A → B → C → A → B → C Each new request goes to the next server. For many systems, that's perfectly reasonable. The interesting part is what happens when the requests aren't equal. Imagine this traffic: GET /health POST /generate-report GET /profile POST /export-large-file GET /products POST /process-video Round Robin might still produce: Server A → 2 requests Server B → 2 requests Server C → 2 requests On paper: A = B = C In production: Server A ███░░░░░░░ 25% Server B █████░░░░░ 48% Server C █████████░ 91% Same request count. Very different workload. One Request Is Not One Unit of Work A health-check request might finish in a few milliseconds. Generating a large report could involve: multiple database queries significant memory CPU-heavy processing external API calls several seconds of execution To a basic Round Robin strategy, both are still: 1 request And that's the trap. We often think we're distributing load . What we're actually distributing is requests . Those are not always the same thing. Servers Aren't Always Equal Either There's another assumption hiding here. Imagine: Server A → 8 CPU / 16 GB Server B → 8 CPU / 16 GB Server C → 2 CPU / 4 GB Sending roughly 33% of traffic to each server probably isn't what you want. That's where Weighted Round Robin helps. A → Weight 4 B → Weight 4 C → Weight 1 The stronger servers receive more traffic. Better. But