Quick answer: Launch traffic is order-of-magnitude higher than beta traffic. A stress test that simulates concurrent peak load on real infrastructure surfaces the bottlenecks that beta can't.
A multiplayer launch is a load test you only get to do once. Practicing it beforehand is the difference between scaling and crashing.
Replay synthetic players
Build a bot framework. Each bot connects, plays a 5-minute session, disconnects. Scale to 2x expected launch peak.
Test the long tail
Sustained 4-hour load beats a spike. Real launches have both; sustained is more likely to expose memory leaks.
Hit every dependency
Auth server, matchmaker, game server, leaderboards, achievements. Each has its own scale curve.
Measure recovery
Kill a server mid-load. How long to detect, reroute, recover? Players notice 30-second outages; aim for 5.
“Launch stress testing isn't optional for multiplayer. It's the rehearsal.”
Run the stress test on production infrastructure, not staging. Surprises hide in the differences.