At 18:00 UTC, a large programming contest hosted by Kattis started. Very soon thereafter, we noticed production issues and started troubleshooting to identify the error. The error was traced back to a database being overloaded, resulting in a long queue of queries and eventual timeouts. Some traffic still worked, but many page loads failed.
Approximately at 19:45 UTC, the overload was traced back to a missing index for a table in the database. At this point, web functionality was fully restored. However, judging had also stalled due to the database being overloaded. Judging has been resumed, but still has a long backlog of submissions to judge. As the large programming contest is also currently ongoing, there is also a significantly increased inflow of new submissions. We apologize for the delay in judging submissions, and our kittens are working at full capacity to get through the queue.
Posted Oct 11, 2025 - 22:22 CEST
This incident affected: Kattis Education (Web) and Kattis Recruiting (Web).