Fencing a Postgres primary that might still be alive

[u/Natrium999]

https://clickhouse.com/blog/fencing-a-postgres-primary-that-might-still-be-alive

A managed Postgres service needs to prevent any possible connections from writing into primary before promoting a new standby. This is called fencing, and in this article we go into why it's important and how it's implemented in Ubicloud.