From around 03:00 BST on 22/06/2020 one of the databases serving our UK diaries began using more resources than normal, which led to reduced performance for diaries. At around 09:10 our engineers began to investigate the problem, and identified a particular query as the cause. At 09:33 they took action to reduce the resource usage of the problem query, and by around 09:50 system performance began to improve again.

We are going to investigate improvements to our alerting as a result of this, as well as whether we need to increase available resources as a result of increased usage of diaries as countries are beginning to recover from COVID-19.