Is this the shortest route served by an Airbus A320? Port Louis to Saint-Denis, 231 km (144 mi). Air Mauritius flight MK248.
This site seems to indicate that they had the shortest route using the A-320 family of aircraft at just over 70km. The page also shows a list of flights, and it looks like one of them is listed at 58km. Based on that list, it looks like your 231km flight wouldn't even break the top 10.
Its difficult to search based on the length of the route and the aircraft type. As far as I can find though, 58km ACE->FUE shortest scheduled route for the A-320.
I don't think so. The shortest route with an A319, which is an A320 family aircraft that I am aware of is Dar es Salaam - Zanzibar (HTDA, HTZA) which if I recall is roughly 73 kilometers (probably even less from airport to airport) operated by FastJet Tanzania.