Throttling limits the number of concurrent calls to a service to prevent overuse of resources. Microsoft Graph is designed to handle a high volume of requests. If an overwhelming number of requests occurs, throttling helps maintain optimal performance and reliability of the Microsoft Graph service.
Throttling limits vary based on the scenario. For example, if you are performing a large volume of writes, the possibility for throttling is higher than if you are only performing reads.
When a throttling threshold is exceeded, Microsoft Graph limits any further requests from that client for a period of time. When throttling occurs, Microsoft Graph returns HTTP status code 429 (Too many requests), and the requests fail. A suggested wait time is returned in the response header of the failed request. Throttling behavior can depend on the type and number of requests. For example, if you have a high volume of requests, all requests types are throttled. Threshold limits vary based on the request type. Therefore, you could encounter a scenario where writes are throttled but reads are still permitted.
The most common causes of throttling of clients include:
The following are best practices for handling throttling:
When you implement error handling, use the HTTP error code 429 to detect throttling. The failed response includes the Retry-After field in the response header. Backing off requests using the Retry-After delay is the fastest way to recover from throttling because Microsoft Graph continues to log resource usage while a client is being throttled.
For a broader discussion of throttling on the Microsoft Cloud, see Throttling Pattern.