Hi,
I am having the same issue, When using normal breezing form capture it takes about 10 seconds to save, When saving a new record from ContentBuilder it takes 2 minutes for a new record and about 40 seconds on a edit record where 2 fields change, This started getting slower after each record that was added. I have 75000 records in the DB. The form is only 30 fields.
I have not tried increase buffer size or anything on the DB.
PHP Version 7.3.33
Joomla! 3.9.23 Stable
BreezingForms 1.9.1 Stable (build 940)