For alternate searches, deprioritise matches that would be between two alternates.

[michael1241]

When two alternate searches are ongoing for the same pairing, lower the priority. This way, more regular players get to play their match, and if any matches aren't played it prioritises those where both regular players were unavailable.

[glbert-does]

similarly, it would probably make sense to assign any searches of pairings that have two open spots the same priority.
what i mean is that e.g. if there are two pairings like that, it doesn't make sense to first fill white for game 1, then white for game 2 next, and only then black of game 1.

so my suggestion would be:

• sort by amount of open spots in the pairing (ascending)
• break ties by last availability_modified_dates per pairing (instead of per player).

late in the season these kind of scenarios are not all that uncommon, so i do think this one would actually be pretty nice to have.