Update 09:24: The incident has been resolved at 09:00 CET, Dec 12. The total duration of the performance degradation was 4 hours and 10 minutes. The problem was caused by an unexpected software fault introduced during routine maintenance. Action was taken to correct the software fault and normal performance was restored.
As of 04:50 CET, Dec 12, both the EU8 and EU9 instance are experiencing performance issues. During a performance degradation, end users are able to access the service, however, some functionality within the service may not be available or running at optimal performance.
Salesforce is currently investigating the cause of the issue. We will keep you updated via this article.
To monitor the performance yourself, you can visit the Trust page provided by Salesforce. You can also subscribe for notifications per instance. On this page you can find the information provided regarding this performance degradation.