Waiting time for new game | Match making

I think something weird is happening in match making:

Lets assume 1v1 RM. Waiting time is almost always around 1,5-2 minutes (my experience on average). I have never had a match without the first 30 seconds, i think even within the first minute. If this is always true for me, it will be also true for my opponent.

So let’s have an example:
I join the match making queue. My (soon to be) opponent joins the queue 10 seconds after me. Then we both have to wait for 90 seconds. And match making makes the match between us.

Why is the following not happening:
I join the match making queue. My opponent joins the queue 10 seconds after me. Almost instantly we got matched and play the game.

I understand the match making is trying to find someone from your own rating. At the lowest (<5%) or highist (>95%) of the players the population is less dense, so finding someone will take some time. That is not the case for me. The difference in elo is max 20 for most games. I feel like this kind of matches dont need 90 seconds waiting time for both players.

So i dont understand this part of the waiting time. Is that just me? Or is this just explainable?

I don’t know anything about the specific implementation of DE’s matchmaking algorithm, but matchmaking algorithms are likely an extension of the Stable Roommates Problem.

The matchmaker probably iterates through all of the players in the queue at pre-defined time intervals (like every 30s, for example), and attempts to make pairs, there are many permutations to test in order to come up with the most balanced pairs (i.e. the “most stable roommates”), so it’s probably not doing calculations each and every second and matching players as soon as they join the queue.

Additionally, the algorithm probably has to take into account people that are queued up for multiple game modes (1v1, 2v2…) and compare pairs across queues to see which is the best match, so maybe the player that just joined the queue that would have been a perfect opponent for you is also a perfect opponent for a team game that you may not be queued up for.

There’s a lot of math and set theory involved in something like this. It’s not easy to come up with a good algorithm and none of them will be perfect, there’s also probably more factors in play aside from ELO that are taken into account, like amount of time in queue, number of games played, and win rate, there may also be limits in place so that you don’t get matched up against someone wildly above or below you, according to the above factors. All of these things will add more waiting time to your queue.


Let me say one thing: This thread isnt meant also complaint about match maker. I am just curious about the algorithm behind match maker. I like algorithms, math, set theory, combinatorics, game theory, … (just to name some words from your post / stable roommates problem page).

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