The meeting point where everyone travels their fair share of the way, computed over the whole Île-de-France transit network.
The geographic midpoint means nothing on public transport. I wrote an engine that looks for the station where everyone’s travel times are closest, taking into account what makes a trip painful, not just how long it takes.
I host MOTIS to compute trips across the whole network. If it goes down, qosqo silently switches to the official IDFM API (PRIM). Checks also catch inconsistent answers: they came from an outage that went unnoticed for 9 days.
The organiser sends a link, each guest adds their starting point, and the result updates live for everyone. No account is needed to take part. Signing in lets you find your trips again without keeping the link. Links expire after 7 days and no personal data goes through the URL.
Behind the scenes, the algorithm does a lot of computing. On screen, only arrival times remain: one recommendation and at most two alternatives. Location is picked up in one gesture. The whole job was hiding the complexity.