We (me and a friend) did something similar for multi city round trips within Europe (https://tripchemy.com).
We created some data structures that allow almost instant searching of such routes and we have scrapers running regularly on Ryanair, easyJet, wizzair, and Transavia. You can query the algorithm here: https://algo.tripchemy.com/routes/TSF?year=2020&month=02&day...
We created some data structures that allow almost instant searching of such routes and we have scrapers running regularly on Ryanair, easyJet, wizzair, and Transavia. You can query the algorithm here: https://algo.tripchemy.com/routes/TSF?year=2020&month=02&day...
It's based on the following Open source project which my friend made back in the day https://github.com/Whazor/Roundtrip