Difference between save and saveAndFlush in Spring data jpa
On saveAndFlush, changes will be flushed to DB immediately in this command. With save, this is not necessarily true, and might stay just in memory, until flush or commit commands are issued.
But be aware, that even if you flush the changes in transaction and do not commit them, the changes still won't be visible to the outside transactions until the commit in this transaction.
In your case, you probably use some sort of transactions mechanism, which issues commit command for you if everything works out fine.
Depending on the hibernate flush mode that you are using (AUTO is the default) save may or may not write your changes to the DB straight away. When you call saveAndFlush you are enforcing the synchronization of your model state with the DB.
If you use flush mode AUTO and you are using your application to first save and then select the data again, you will not see a difference in bahvior between save() and saveAndFlush() because the select triggers a flush first. See the documention.