Persistent 429 Throttling on CSOM/REST despite Exponential Retry Logic

Question

"429 Too Many Requests" errors when performing bulk metadata updates on a SharePoint Online library (~200k items). Despite implementing exponential backoff (retry-after logic), the throttling persists, eventually resulting in 503 errors and session termination.

Answer 1

Hi Meadows Bali

Thank you for reaching out to Microsoft Q&A forum

As states in Avoid getting throttled or blocked in SharePoint Online, in this context, to mitigate this behavior, Microsoft recommends reducing the overall pressure placed on the SharePoint Online service rather than relying solely on retries. This includes breaking large metadata update jobs into smaller batches, significantly lowering concurrency, and honoring the Retry-After header returned with 429 or 503 responses.

Bulk update operations should be spread across multiple execution windows instead of running in a single continuous session and scheduled during off-peak hours to reduce contention. Continuing to retry aggressively or restarting jobs immediately after throttling can prolong the blocked state and lead to sustained 503 responses.

Unfortunately, currently, there is no supported way to disable or increase throttling limits for customer workloads, so long-running bulk updates must be deliberately paced to remain within service limits.

Kindly let me know in the comments for further support

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