If this system fails, the game becomes a frustrating, unplayable mess that bleeds players instantly.

This article explores how developers design these algorithms to keep queue times short while maintaining a competitive environment.
Trophy and Rating Systems
The algorithm's primary goal is to match you against someone with the exact same—or very similar—trophy count.

This is why winning streaks inevitably end in a 'wall' of difficult matches; the system is functioning exactly as intended.
The algorithm does not care what deck you are playing.With millions of players, you will occasionally draw a bad matchup.It helps them learn before facing real humans. The Free-to-Play Dilemma
The standard Elo system works perfectly for chess because all pieces are equal, but tower rush games feature upgradeable cards.

The system will try its best to match you with someone who has the same trophies AND a similar tower level.
System PriorityImportance LevelTrophy CountThe system will always prioritize finding an opponent within a 50-trophy rangeKing Level / Card LevelsSecondary Priority Maintaining Competitive Integrity
By artificially capping all card levels to a specific number, the algorithm can rely purely on the Elo rating.

When levels are equalized, the matchmaking system shines, ensuring that the better player almost always wins.