Processing and order
Hooks are batched and processed every 5 seconds, ordering is not guaranteed and the time stamp should be checked by the subscription handler.
There is no limit to the number of subscriptions or hooks that can be created but creating a large amount of subscriptions to the same hook can result in a delay.
If a subscription fails, such as the URL being unavailable, retries are not made. If a URL consistently fails it may be grey listed for a short period of time, start at 1 minute and doubling each time until 1 day is reached.