Loading deals and associating with contacts




I’m looking for the best way to import historical bookings & quotes (roughly 100K to 300k per account) and append to contacts within HubSpot but then also set up an API to import new bookings & quotes and append to existing contacts/ set up new contacts as required. We would need the details of these bookings & quotes to be available to filter in list creation although I understand they couldn’t be used for personalisation tokens.

Which would be the best API to use to do this and would this handle the appending to the correct contacts as I have no wish to do this manually!

thanks a lot for any advice supplied