Customize the match algorithm - Amazon GameLift
Add pre-batch sortingPrioritize backfill ticketsFavor older tickets with expansions

Customize the match algorithm

FlexMatch optimizes the default algorithm for most games to get players into acceptable matches with minimal wait time. You can customize the algorithm and adjust matchmaking for your game.

The following is the default FlexMatch matchmaking algorithm:

  1. FlexMatch places all open matchmaking tickets and backfill tickets in a ticket pool.

  2. FlexMatch randomly groups tickets in the pool into one or more batches. As the ticket pool gets larger, FlexMatch forms additional batches to maintain optimal batch size.

  3. FlexMatch sorts the tickets by age, within each batch.

  4. FlexMatch builds a match based on the oldest ticket of each batch.

To customize the match algorithm, add an algorithm component to your rule set schema. See FlexMatch rule set schema for the complete reference information.

Use the following optional customizations to impact different stages of your matchmaking process.

Add pre-batch sorting

You can sort the ticket pool before forming batches. This type of customization is most effective with games with large tickets pools. Pre-batch sorting can help speed up the matchmaking process and increase player uniformity in defined characteristics.

Define Pre-batch sorting methods using the algorithm property batchingPreference. The default setting is random.

Options for customizing pre-batch sorting include:

  • Sort by player attributes. Provide a list of player attributes to pre-sort the ticket pool.

    To sort by player attributes, set batchingPreference to sorted, and define your list of player attributes in sortByAttributes. To use an attribute, first declare the attribute in the playerAttributes component of the rule set.

    In the following example, FlexMatch sorts the ticket pool based on players' preferred game map and then by player skill. The resulting batches are more likely to contain similarly skilled players who want to use the same map.

    "algorithm": {
    "batchingPreference": "sorted",
    "sortByAttributes": ["map", "player_skill"],
    "strategy": "exhaustiveSearch"
},

  • Sort by latency. Create matches with the lowest available latency or quickly create matches with acceptable latency. This customization is useful for rule sets forming large matches of more than 40 players.

    Set the algorithm property strategy to balanced. The balanced strategy limits the available types of rule statements. For more information, see Design a FlexMatch large-match rule set.

    FlexMatch sorts tickets based on players' reported latency data in one of the following ways:

    • Lowest latency locations. The ticket pool is pre-sorted by the locations where players report their lowest latency values. FlexMatch then batches tickets with low latency in the same locations, creating a better game play experience. It also reduces the number of tickets in each batch, so matchmaking can take longer. To use this customization, set batchingPreference to fastestRegion, as shown in the following example.

      "algorithm": {
    "batchingPreference": "fastestRegion",
    "strategy": "balanced"
},

    • Acceptable latency matches quickly. The ticket pool is pre-sorted by locations where players report acceptable latency value. This forms fewer batches containing more tickets. With more tickets in each batch, finding acceptable matches is faster. To use this customization, set the property batchingPreference to largestPopulation, as shown in the following example.

      "algorithm": {
    "batchingPreference": "largestPopulation",
    "strategy": "balanced"
},
    Note

    The default value for the balanced strategy is largestPopulation.

Prioritize backfill tickets

If your game implements auto-backfill or manual backfill, you can customize how FlexMatch processes matchmaking tickets based on request type. The request type can be a new match or backfill request. By default, FlexMatch treats both types of requests the same.

Backfill prioritization impacts how FlexMatch handles tickets after it batches them. Backfill prioritization requires rule sets to use the exhaustive search strategy.

FlexMatch doesn't match multiple backfill tickets together.

To change prioritization for backfill tickets, set the property backfillPriority.

  • Match backfill tickets first. This option tries to match backfill tickets before creating new matches. This means that incoming players have a higher chance of joining an existing game.

    It's best to use this if your game uses auto-backfill. Auto-backfill is often used in games with short game sessions and high player turnaround. Auto-backfill helps these games form minimum viable matches and get them started while FlexMatch searches for more players to fill open slots.

    Set the backfillPriority to high.

    "algorithm": {
    "backfillPriority": "high",
    "strategy": "exhaustiveSearch"
},

  • Match backfill tickets last. This option ignores backfill tickets until it evaluates all other tickets. This means that FlexMatch backfills incoming players into existing games when it can't match them into new games.

    This option is useful when you want to use backfill as a last-chance option to get players into a game, such as when there aren't enough players to form a new match.

    Set backfillPriority to low. 

    "algorithm": {
    "backfillPriority": "low",
    "strategy": "exhaustiveSearch"
},

Favor older tickets with expansions

Expansion rules relax match criteria when matches are difficult to complete. Amazon GameLift applies expansion rules when tickets in a partially completed match reach a certain age. The creation timestamps of the tickets determine when Amazon GameLift applies the rules; by default, FlexMatch tracks the timestamp of the most recently matched ticket.

To change when FlexMatch applies expansion rules, set the property expansionAgeSelection as follows:

  • Expand based on newest tickets. This option applies expansion rules based on the newest ticket added to the potential match. Each time FlexMatch matches a new ticket, the time clock is reset. With this option, resulting matches tend to be higher quality but take longer to match; match requests might time out before completing if they take too long to match. Set expansionAgeSelection to newest. newest is default.

  • Expand based on oldest tickets. This option applies expansion rules based on the oldest ticket in the potential match. With this option, FlexMatch applies expansions faster, which improves wait times for the earliest matched players, but lowers the match quality for all players. Set expansionAgeSelection to oldest. 

"algorithm": {
    "expansionAgeSelection": "oldest",
    "strategy": "exhaustiveSearch"
},