Ep #41: Latency in the Real World – How Distance, Fiber Routes, and Undersea Cables Affect the Apps We Use Daily
Why a call feels awkward, a game feels unfair, and a trade makes or breaks millions - all because of latency.
Ep #41: Breaking the complex System Design Components
By Amit Raghuvanshi | The Architect’s Notebook
🗓️ Sep 20, 2025 · Weekend Special Post ·
In 2010, a mysterious construction project began in the Pennsylvania countryside. Workers weren't building another shopping mall or housing development, they were digging a perfectly straight trench from Chicago to New Jersey. The project cost $300 million and had one singular purpose: to shave 3 milliseconds off the time it took financial data to travel between the Chicago Mercantile Exchange and NASDAQ in New York.
This wasn't just any construction project. It was the creation of the fastest fiber optic cable in the world, and those 3 milliseconds were worth billions in high-frequency trading advantages. Welcome to the real world of latency - where the speed of light itself becomes a business constraint, and every millisecond counts.
Why Latency Feels So Personal
Latency is just a delay, measured in milliseconds. But in the real world, those milliseconds translate into human experience.
Video calls: More than 150 ms delay feels unnatural in conversations.
Online gaming: Anything beyond 50–100 ms can make you lose a battle before you even see it.
Stock trading: A few milliseconds can mean millions gained or lost.
Streaming apps: Latency isn’t about watching - it’s about starting. If Netflix takes 5 extra seconds to load, people drop off.
Latency is the invisible tax we all pay, and It’s not bad design, it’s the reality of a world connected by wires, satellites, and the limits of physics. Curious how this affects you? Try pinging a server far away (like from New York to Tokyo) and see how those milliseconds add up!
The Geography of the Internet
One of the biggest myths is that the internet is “in the cloud.” In reality, it’s under the ocean.
There are over 500 undersea cables carrying 99% of international data. They’re as thick as a garden hose, laid down by specialized ships, and they connect continents together like a nervous system.
A few mind-bending facts:
A fiber optic signal travels at about 200,000 km/s in glass, two-thirds the speed of light in vacuum.
The shortest path is not always a straight line. Cables follow seabed terrain and safe landing stations, which makes them longer than “as the crow flies.”
One of the busiest cables, the MAREA cable, stretches 6,600 km between Virginia and Spain, carrying data for Microsoft and Facebook with 200 terabits per second capacity.
Every time you stream a YouTube video from another continent, your packets are swimming through one of these cables. And each hop adds delay.
The Geography of Speed
Most people think the internet is instant, but physics has other plans. When you tap "Send" on a WhatsApp message from Mumbai to your friend in San Francisco, your data doesn't teleport, it embarks on an epic 15,000-kilometer journey that reveals the hidden architecture of our connected world.
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