The incident has been resolved. The cause was one database server being under heavy CPU load - that caused database queries to either take a long time to complete or fail altogether for Grafana Cloud instances using that specific database server. As an outcome, it made some instances unavailable, and it also made new instance startups fail.
We were made aware of an issue affecting a significant subset of PrivateLink customers not supporting HTTP/2. This issue persisted from ~14:45 UTC to 18:20 UTC. Customers affected may notice a gap in their data during this time.