Adding and Updating large numbers of contacts efficiently
The batch activity endpoints allow you to add or update up to 20,000 contacts by making either 1 or 2 API calls.
Add and Update up to 20,000 contacts with a single API call
This process imports all contacts in your local application or database to Constant Contact, regardless of whether they are:
a new contact
an existing contact whose information has changed locally
an existing contact whose information is unchanged.
You do not need to filter or compare contact data in Constant Contact with your local data. The only property that will change for contacts whose data was unchanged locally is that the modified_date property, which reflects the time of the import activity.
Do this as follows:
Collect the contacts you are looking to import from your application or database through whatever query or filtering method(s) you support. Make sure to then format these contacts into one of the supported file formats.
When executed, all contacts are imported into Constant Contact:
Any new contacts are added to the appropriate contact list(s).
All existing contacts are technically updated (modified_date will reflect the time of the import activity); however any contacts whose data was unchanged locally, remain unchanged in Constant Contact.
Add and Update a maximum of 20,000 contacts using 2 API calls
This batch import process updates only new contacts or existing contacts whose information has changed using only 2 API calls, one to export the contacts from Constant Contact, and one to import them back in.