SmartSurvey batches events for each webhook URL and POSTs approximately every minute. If the webhook URL doesn't return a 200 HTTP response code, that POST request will be re-attempted up to 72 times at 20 minute intervals (1 full day).

If a particular POST request is unsuccessful and is being retried, no other POSTs will be attempted until the first one succeeds or ultimately fails (after 72 attempts). Subsequent events are batched and deferred until the first completes. Once the first batch completes, deferred batches will be processed sequentially (maximum of 1,000 events per batch).

Since webhook requests can ultimately fail, it's best to accept and store data (with an HTTP 200 response to SmartSurvey) for later processing to avoid data loss.