The network latency seems to have stabilized but is still higher than usual, and the network maintenance is still underway. The posted maintenance window is 2021-12-15 20:00 UTC+0 – 2021-12-16 15:00 UTC+0.
해결됨:
The hosting provider has completed the scheduled maintenance (https://status.hetzner.com/incident/b90d7054-17af-4eae-a861-7ea9bfc489db).
The network latency between Frankfurt and Falkenstein is back to normal levels (5ms ICMP ping, 10ms for a complete HTTP request).