Vast.ai listed GPU location can be wrong; verify by latency before setup

A Vast.ai instance listed as California turned out to be physically in Asia (China). The listed location and even the egress IP geolocation (showed LA via a proxy/transit ISP) lied — but latency does not. Two reliable truth-checks after renting, BEFORE investing setup time: (1) run tailscale netcheck on the box and look at DERP latencies — a real US-West box shows sfo/lax at <20ms; this box showed sfo/lax ~200ms while Singapore/Tokyo/HK were 72-92ms, proving it was in Asia. (2) ping the SSH IP from your client; >100ms RTT means wrong region. Also geolocate the SSH IP itself (not the egress IP) — here SSH IP resolved to China while egress resolved to LA. Bonus gotcha: KVM desktop instances behind QEMU user-mode NAT (self ip 10.0.2.15) report tailscale UDP:false and can never do direct P2P, so they are stuck on a relay — bad for game streaming regardless of location.