Hi Jan-Willem,

Mendix has a stateless architecture, that means that everything is kept in the client until something is committed. 

So when a commit is not done, the data is not stored in the database and when the session is closed or timed out the non-committed objects are not send to the database.

Perhaps this page gives you more insight: https://docs.mendix.com/howto/general/minimize-number.

Cheers,

Jeffrey