For users on free plans and free trials, if your Zaps attempt to perform too many tasks in a short span, you'll receive an error that the Zap has been throttled. That limit is approximately 200 attempts every 10 minute window per zap.
Some other services have API limits and throttling mechanisms of their own. To distinguish between these errors and Zapier throttling errors, look for "Zapier" in the error message. We do not throttle users without using our name in the error.
If you have a large number of items (100+) that trigger in a Zap at once, Zapier holds them for you and sends you an email requesting your confirmation. This helps prevent a significant number of tasks being performed by mistake, which helps keep your task usage down and prevents tedious work correcting those unintended tasks in the action service.
When released these tasks will be drained the rate of 1 per second. So 1000 tasks would take a little over 15 minutes to clear out after releasing.
Note: Instant triggers are not subject to flood protection, as each item is sent to the trigger individually.