We have around 15000 subscribers and send out a monthly statement. This statement includes a custom field called Monthly Points.
This custom field should reset to 0 at the end of each month so I'm looking at the best way to do that. The 2 options I found so far are:
OPTION 1: use the API subscriber import function to update the custom field of all subscribers. This requires multiple API calls and requires a lot of server resources for so many subscribers.
OPTION 2: use the API to delete the custom field and re-create the same custom field. With the test I've done so far it looks like that when a custom field is deleted, all related values for each subscriber are also deleted. So when you re-create the same custom field again, all values are reset to nothing. For all users that won't have any points at the end of the month, I use fallback=0 in the email to display 0.
I prefer OPTION 2 as it requires only 2 quick API calls.
What do you think about OPTION 2. Do you see any issue with deleting/re-creating a custom field every month?
Your suggested solution sounds good. That's how I'd do it.