As I commented here initially: T119736#2445587
Since 2016-07-05 at 23h UTC (probably, a software deploy) there is high rate of Lock wait timeout exceeded; try restarting transaction (10.64.16.30). This host is centralauth master and the queries are CentralAuthUser::saveSettings:
https://logstash.wikimedia.org/#dashboard/temp/AVXVMNhAw3dCNxx2bE7U