How you get at the next primary key is a separate issue from MMF. Some developers us an ID table that contains the next id to use for each table. The table is locked while the next key is extracted to avoid any concurrency issues. If you find the next id from the actual table, you will need to manually deal with concurrency issues.

>If I use HookPreSave, does that mean I have to make a separate SQL call to retrieve the current highest primary key? Will I also have concurrency issue since someone else might be adding at the same time?