EventLogging suffered from performance problems and data loss from Tuesday 2015-05-05 22:00 UTC to Wednesday 2015-05-06 20:00 UTC (22 hours).

During that period, an exceptional amount of events were sent to EL server for a given schema. The system could not handle them properly, and this caused data loss (30%-40% during the period) and some small gaps in the db. All schemas were affected.

The missing data will be backfilled during this week.

Phab Task: https://phabricator.wikimedia.org/T98588
Incident documentation: