Alexandre's place is in a great neighborhood to base out of in Paris. The 4 story walk up is no joke and the place is pretty tight quarters. We were three adults and I'd say four would be pushing it! Probably perfect for two.
The water heater is small, so spreading out showers is a good idea and if you want to do laundry, have a translator on hand if you don't speak French :)
Overall a lovely stay and a good workout walking up to the flat!