What is Round-Robin

Round-robin is a load balancing algorithm that sends each incoming request to the next server in a fixed sequence. With servers A, B, and C, requests go to A, then B, then C, then back to A.

How it works

The load balancer maintains a pointer to the current server. On each request, it advances the pointer and forwards the request to that server. When it reaches the end of the list, it wraps around to the beginning.

Weighted round-robin assigns different weights to servers. A server with weight 3 receives three requests for every one that a server with weight 1 receives. This accounts for servers with different capacities.

Why it matters

Round-robin is the default algorithm for most load balancers because it is simple, predictable, and fair when servers have equal capacity and request costs are similar. It breaks down when requests have very different processing times — a server handling an expensive query gets the same number of new requests as one handling fast lookups. In those cases, least-connections or least-response-time algorithms adapt better.

For the full set of algorithms and when to choose each one, see How Load Balancing Works.