When you create an organization, the data storage region picker now offers AWS us-east-1 (N. Virginia) next to Oregon, Ireland, and the Netherlands. US customers had asked for an east-coast region.
Each region is a card showing the cloud it runs on, the place, and the cloud's own region ID. Dash0 stores that organization's telemetry in the region you pick, and you cannot change the region once the organization exists. Organizations that already exist keep the region they were created in.
See Organizations for the full region list and what the choice affects.