Data Locality & Geo-Distribution

No software optimization, compilation flag, or algorithm can surpass the speed of light.

The Physical Constraints of Fiber Optics:

• Light travels through a vacuum at c = 300,000 km/s.
• In silica glass fiber optic cables, the refractive index (n ≈ 1.5) slows photons down to:

v = \frac{c}{n} ≈ 200,000 km/s \quad (5 microseconds per kilometer)

• Because subsea cables must traverse continental shelves, mountain ranges, and avoid deep ocean trenches, physical fiber paths are 1.5× - 2.0× longer than great-circle geographic distances.
• Optical repeaters, erbium-doped fiber amplifiers (EDFAs), and BGP router hops add additional switching latency.

Empirical Round-Trip Times (RTT):

• London ≤ftrightarrow Frankfurt: ~ 15 ms (700 km)
• New York ≤ftrightarrow San Francisco: ~ 70 ms (4,100 km)
• New York ≤ftrightarrow London: ~ 75 ms (5,500 km)
• San Francisco ≤ftrightarrow Tokyo: ~ 110 ms (8,200 km)
• London ≤ftrightarrow Sydney: ~ 280 ms (17,000 km)

If a user in Sydney accesses an API hosted exclusively in a single US-East (Virginia) datacenter, every single network roundtrip suffers an unavoidable 220 ms delay before the server begins executing code.