We’ll be upgrading from SQL 2017 to SQL 2019 on our primary clusters between 9:00-10:00AM Eastern (14:00-15:00 UTC) on March 7, 2020. We expect to be read-only less than an hour and in full maintenance mode only a few minutes. For more details, see our post on meta.stackexchange. If we’re in maintenance and you can’t see that post, try again in a few minutes!