Estimate a 0330 hr pickup in Aix for international flight out of Marseille airport. Are taxis or Uber readily available at that hour? Is it possible to book a pickup time in advance?
That is a common thing; assuming that you do not live in Aix you can ask the local people a day or two before at the place you are staying at to hook you up with transport to the airport; or if you do not trust that option, stay at a hotel, airbnb, hostel, etc. near the airport the night before your red eye
We had this experience at the end of the RS Eastern France tour. We had the hotel arrange a cab to pick us up. The cab was there on time. It was expensive at 72Euro, and we couldn't share with any other tour members because no one else was returning that early in the morning.
Personally I wouldn't want the stress of relying on a car service or any other transport to get me there. I'd stay in a hotel as near to the airport as possible.
The Marseille-Provence airport maintains a very useful website: https://www.marseille-airport.com/
Look under Access.
The airport is about a half-hour bus ride from the Aix bus station. Mid-way it stops at the TGV high-speed-train station. But the last bus is just before midnight.
There is no direct train connection between Aix and the airport. Going by train from Aix to either Avignon or Marseille to connect to an airport train is far out of the way and the trains don't run in the early morning hours anyhow.
The airport has an official taxi service and estimates the night fare from Aix at 60 euros plus possible surcharges. The site offers on-line reservations.
Your hotel should know if there are alternative pick-ups.
Google Maps will show you a cluster of hotels a couple of kilometres from the airport terminal. Probably too far to walk in darkness with luggage, so you would still need to hire a ride.
Just confirming it is International flight / out of Schengen area?
If not you can definitely arrive later.
Either way I would take and trust a private car service / professional taxi service for this without worry ; they do this for a living and understand airport timing.
If you are staying at a decent hotel, ask them to make the arrangements for you when you check-in.
It is a 30 minute car ride, staying at an airport hotel rather than a 30 minute distance is paranoia. There will be zero traffic. The airport in Marseille is not in the city and easy to drive to.