TL;DR

For around three hours on November 6th, 2025, Buttondown's API faced severe availability issues. The root cause of these issues is that our analytics caching fell behind, meaning that the analytics data associated with emails, such as number of clicks, deliveries, etc., was not being cached on the email, meaning that they were getting calculated in band for emails accessing the analytics endpoint. This, coupled with the fact that we had an errant code path on the email completion modal that would fairly aggressively pull the API every few seconds without exponential backoff on failures, meant that we drowned ourselves in redundant requests for a very computationally expensive operation.