Real-time game matchmaking

Design a real-time matchmaking service for an online multiplayer game with 5M daily players that pairs players into balanced matches in under 30 s while keeping per-player network latency to the chosen game server low. It must balance skill (fair matches), latency (low ping), and queue time (don't make people wait). How do you run the queue, pick servers near players, and resolve the inherent tension between these goals?