France is holding a run-off presidential election on Sunday, April 24. Each polling place has approximately 1,000 registered voters. During the day, poll workers at each polling place take note when 100 ballots have been cast. At that point the ballots are retrieved and sent to the counting station. This is repeated, each time another 100 ballots have been cast. Therefore, because the bulk of the counting is done during the day, the votes will have been counted within an hour and thirty minutes of the closing of the polls.
In the U.S., in which almost all public elections are on Tuesday, there is a glut of voters in the evening, because many people work on Tuesday during the normal business hours and then vote when they leave work in the evening. But in France, and many other countries, the flow of voters to the polling station is more evenly-spaced, because most people don’t work on Sundays.
France has no postal ballots, but France allows proxy voting. French citizens living in possessions of France have the same voting rights and the same procedures for in-person voting. French citizens living overseas, in parts of the world that are not French possessions, vote at French government offices such as consulates. See this article for more about proxy voting.