Webhooks v/s polling for all users drives' within an Org (multi-tenant) - MS Graph

Question

We are going to have a multi-tenant application that is going to be scanning files for each user per organization for multiple orgs. We would like to get notification if any user uploads/changes a file in the drive. There are at-least 2 options to retrieve those: either store delta link for each user and poll periodically to get the change or subscribe using webhooks to get notification on change. If we have 10k+ users, I am not sure if the first option is feasible. For the latter one, my only concern with webhook is do I have to register for each user separately? ie., does the resource need to be /users//drive/root or should it just be /drive/root? Since there is a limitation of no. of webhooks per app/tenant, I am not sure if creating webhooks for each user is a right approach.

Please advise.

Answer 1

The limitation applies to the users/groups objects (i.e. if you wanted to subscribe to users/groups being updated), not to the drives.

Yes, you need to subscribe to each drive individually, and to renew the subscriptions individually as well. If you want to save the number of roundtrips, you can group those operations in a batch.

You can also combine the delta + webhooks: do the initial sync with delta and store the token, register your webhook. And then trigger querying the delta link upon receiving a change notification. This way you get the best of both features and avoid regularly polling delta when there might not be any change.