Latency Myth-Busting: Why “<50 ms Global Median” Is Science-Fiction
Think of the moment your game bumps the leaderboard, your telehealth app raises a vitals alert, or your auction platform shouts “new bid!” — that’s an event racing around the planet. Some vendors plaster banners claiming “< 50 ms global latency.” Cute slogan… if you’ve cracked faster-than-light travel.
Physics Doesn’t Read Marketing Copy
- Speed-of-light reality: Light needs ~74 ms just to lap halfway around the Earth in a vacuum. Fiber is ~30 % slower, so best-case one-way transit is ~100 ms.
- Routers, switches, TLS handshakes, congestion control all layer extra time.
- Result: any “<50 ms global median” claim either (a) quietly drops the far-side of the planet from its math, or (b) counts only the hop inside one cloud region.
What PubNub Measures (and Publishes)
Our status page shows the metrics we actually control:
Those numbers come from a constant stream of synthetic publishers/subscribers, not cherry-picked demo traffic. We run internal alerts to stay honest by alerting the moment a cluster drifts above its SLA. And our auto-scaling, Kubernetes-based infrastructure adds capacity instantly, to keep latency low.
Where the Rest of the Latency Lives
We can’t shrink the distance between a device on rural 4G and the nearest PoP, nor can any provider. That “last-mile” hop is the bulk of user-perceived latency (often 50-200 ms). Pretending it vanishes doesn’t help engineers design responsive apps; owning the part we do control does.
How the <30 ms Banner on PubNub.com Holds Up
That badge refers to the time your event spends inside our fabric — from first byte at the edge to last byte fanning out to subscribers in-region. It’s the part we instrument six ways from Sunday.
Spotting Hand-Wavy Benchmarks
Ask for the map. If a vendor says “global,” demand the list of probe locations. Running tests between three U.S. zones ≠ “global.”
Look for the three hops:
- Client ➜ PoP (variable, ISP-dependent)
- PoP ➜ PoP (provider-controlled)
- PoP ➜ Client(s) (variable again)
Check the percentile. Medians hide the 49 % of messages that are slower. We track p50, p90, and p99 because tail latency breaks real-time UX.
Verify continuous measurement. One-off white-paper numbers age like sushi.
Designing for Real-World Latency
- Minimize distance: PubNub automatically picks the PoP closest to your users; and we have PoPs around the world.
- Stay event-driven: Fire-and-forget Publish lets your backend move on while we push to every subscriber.
- Exploit edge compute: Run Functions < 10 ms from ingress to filter, translate, or enrich events before they hit the wire.
- Plan for the worst tail: Optimistic UIs, retries, and idempotent handlers keep UX snappy even when someone’s on hotel Wi-Fi.
Bottom Line
Latency math isn’t marketing poetry. The laws of physics set the floor; engineering discipline sets the ceiling. PubNub owns the piece in the middle — single-digit milliseconds in-region, transparent dashboards, no warp drive required.
Ready to test it yourself? Spin up a free key and watch your subscribers light up before you can blink. If anyone tells you they beat the speed of light, ask for the patent number.
