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We used Live stream API to create live broadcast events, but it hit userRequestsExceedRateLimit when create live broadcast (POST /liveBroadcasts/insert). And Docs didn't specify any exactly rate limit number. Can help us to find max rate limit ，5 requests/sec or 8 requests/sec?
Here is error message (request rate 10/sec)
{
code:403,
errors:[{
domain:"youtube.liveBroadcast",
reason:"userRequestsExceedRateLimit",
message:"User requests exceed the rate limit."
}]
}

The official docs on rateLimitExceeded say:
The request was sent too quickly after the previous request. This error occurs when API requests to retrieve messages are being sent more frequently than YouTube's refresh rates, which unnecessarily wastes bandwidth and quota.
Every request to the YouTube API has a cost and rate limit, all of which add towards your quota. You can use a tool such as the YouTube Bulk Reports API to track your requests to see which ones in particular are causing you to go over your quota. All Live Streaming API calls (write operations) cost about 50 units. You can check the quota available to your application in the Developers Console.
In the Developers Console under YouTube Data API v3, make sure your "Per-user limit" under "Quotas" is set to the maximum value of 3,000 requests/second/user. If you're going over that, you will need to contact Google to increase your quota.