Is there a need to throttle requests to the AMP ping url? I have an infrequent case where a page change may need to update the cache for about 20,000 urls. The documentation does not indicate if requests to the ping url should be throttled though.
In my case, the requests would be made in serial, so I doubt the load would be any issue. I just want to be sure it's allowed and I don't start getting rejected for exceeding an undocumented limit.
I think it is ok, just don't let your AMP hit the quota limits. Just remember that the AMP URL API has a quota of 1,000,000 Request per day and 1,000 Request per 100 seconds, you can also check it in this Usage Limits. You can double check it in your Developer Console. For more information, check this thread about AMP Cache