Hi @Alex ,
This is by design and throttling expected behavior while using OneDrive, OneDrive for business, and SharePoint Online irrespective of APIs.
When a user exceeds usage limits, SharePoint Online/ OneDrive throttles any further requests from that user account for a short period. All user actions are throttled while the throttle is in effect.
For requests that a user performs directly in the browser, OneDrive/SharePoint redirects you to throttling information page, and the requests fail. For all other requests, including CSOM or REST calls, OneDrive/SharePoint returns HTTP status code 429("Too Many Requests") or 503("Server Too Busy") and the request will fail.
There is no specific limits for OneDrive/SharePoint, Service limits for OneDrive, OneDrive for Business, and SharePoint Online are not available.
Please refer to this article for additional information:throttling
Hope this helps,
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