If your data must stay in the EU, pass withHosting("eu") exactly; any other string, including a typo, silently falls back to US hosting with no error. Verify the region in the dashboard after first sync rather than trusting the call. For caching control, provide a custom storage implementation to decide how flag values persist between fetches; the default storage may not suit short-lived containers or serverless functions. Test flag changes end to end in the target region before relying on residency.

Context: Official docs (CloudBees, Java API): documents the region gotcha: withHosting("eu") selects the EU hosting region, and any other value silently falls back to US hosting. A custom storage implementation controls how flag values are cached.