At around 18:43 Zurich time, Proton experienced a partial service degradation due to a hardware failure. Because of our redundant infrastructure, no data or emails were lost, but some users were unable to access Proton services for 10-15 minutes.
The root cause is related to the poor performance of certain Redis cluster nodes under high memory use. Corrective action and mitigation put in place since yesterday enabled us to limit the impact of the incident.
We are taking additional corrective action to make this type of issue less likely to happen in the future. We apologize for the inconvenience and thank you for your patience.