There was a major outage of frontend sites that was caused by failed communication with Memcached servers.
Cause behind the issue is still being investigated, but all systems are now operational.
Timetable:
https://www.worldtimebuddy.com/edt-to-utc-converter?qm=1&lid=5,100,792680&h=5&date=2018-8-1&sln=4.7-5.9