Choosing a Hosting Region: When Latency Matters and When It Doesn't
Every provider asks which region you want, and most people pick the default or the one nearest themselves. Both are sometimes wrong: the right answer is nearest your users' data path, and how much that matters depends entirely on what you're serving.
The physics is fixed: round-trip latency runs roughly 1ms per hundred kilometers of fiber, so New York to Frankfurt costs ~80ms and no engineering removes it. What matters is the multiplier. A static page behind a CDN pays the distance once or not at all. A server-rendered page that makes four sequential database queries pays it repeatedly. An API called in a loop pays it on every call. The same 80ms is invisible in the first case and user-visible sluggishness in the last.
Practical picks: if your users are one-country concentrated, host there or at the nearest major hub and be done. If they're global but the app is read-heavy content, host anywhere sensible and let a CDN do the geography. That covers most sites. The genuinely latency-sensitive middle (interactive dashboards, collaborative tools, anything conversational) is where region choice is a real product decision, and where Fly.io-style multi-region app hosting earns its complexity.
The rule that saves the most pain: keep the app and its database in the same region, always. Cross-region database calls stack per-query latency into every request. The classic mistake is a Frankfurt server dutifully querying a Virginia database, adding 90ms four times per page. Multi-region done right replicates data close to each app instance. Done wrong, it's distributed slowness.
Two non-latency reasons to care. Compliance is one: EU data-residency requirements make region a legal question, and Hetzner, Scaleway, and OVHcloud build their pitch on EU hosting. Price is the other: several providers charge measurably more in some regions (Hetzner's US locations, most providers' Asia-Pacific), so the same server costs different money in different places.
Provider pages list region counts, and the guides on bandwidth and static hosting cover the CDN half of the geography problem.