Our team has identified a bug in the handling of global and label frequency cappings which meant they were not properly applied and users received more push notifications than intended. This only affected trigger campaigns and transactional push notifications, push campaigns were not affected.
This bug was introduced the 2022/01/31 around 16:00 UTC and a fix was deployed the 2022/02/09 around 18:00 UTC.
The root cause was an upgrade in a internal library which handled fetching the frequency data for each user; while rewriting code during this upgrade process the semantics of an important function were changed by mistake and this caused the function to no longer work as intended, thus causing the bug.
As soon as we were made aware of the bug our team investigated and quickly deployed a fix. As of the 2022/02/09 around 18:00 UTC all frequency cappings work as expected again.
While this internal library has a significant number of tests, we found that some functions are not properly unit tested. In the future we will work on improving unit and integration tests for this library.