Aah yes... that magical "zero-downtime" cloud, lots of promises are made by the cloud providers in that area but all eventually broken at some point. Its a fact of life with technology unfortunately. :)
No need for the cloud with ScyllaDB[1], CockroachDB[2] and others all being used in production.
LetsEncrypt chose their setup for perfectly valid reasons they described on their blog[3]. Please describe your expertise for saying they're "doing it wrong", because its clear from their blog they put a lot of time thinking about it.
[1]https://www.scylladb.com/ [2]https://www.cockroachlabs.com/ [3]https://letsencrypt.org/2021/01/21/next-gen-database-servers...