Weighted round-robin accounts for servers with different capacities. A server with weight receives times as many requests as a server with weight .
If server A has weight and server B has weight , the rotation is: A, A, B, A, A, B.
The algorithm still runs in time for each request selection. Space complexity is for server list plus weights.
Use weighted round-robin when mixing server sizes. Your -core machine can handle more traffic than your -core machine. Set weights accordingly.