Hello @mgr,
Thanks for sharing your question with the Klaviyo Community!
If you were attempting to use API to update the profile properties of 500 individual contacts/profiles, this would need to be done with 500 separate calls. This is because you would need to include the PERSON_ID as the target of these calls you are making.
An alternative you can use to batch update profile properties at once would be to using .CSVs. Using a .CSV, you can bulk update the profile properties for contacts by including email address, the profile property and the new profile property value you wish to update in the .CSV you are importing/uploading to Klaviyo. You can learn more about this strategy from the Klaviyo resources below:
I hope this helps!
David