Starlink system design: how internet reaches your home

Starlink is thousands of small satellites, roughly 500 km up, talking to a dish that never physically turns. That is the whole shape of the answer. The rest is why each piece looks the way it does.

This is the standard explanation you'd give in a system design interview. It isn't Starlink's internal design.

Why one big satellite fails

When Starlink India comes up in conversation, the first guess is usually one big satellite sitting far above. The obvious version of that idea puts it around 36,000 km up. The path is dish, far satellite, ground, and the signal arrives late. Reject it.

Distance is the cost here. A satellite that far away makes every round trip slow. So the design goes the other way and brings the satellites close.

The answer is about 500 km. Closer means faster, and it also means many satellites instead of one.

The catch with being low

A satellite at that height doesn't hold still over your house. It moves on, and it's gone in minutes. A single satellite at 500 km would give you a connection that vanishes almost as soon as it starts.

That's the reason for the numbers. You need hazaaron chhote satellites, so that when one leaves, another is already there.

Why the dish doesn't turn

If the satellites keep moving, you'd expect the dish to swing around and chase them. It doesn't. Inside the dish are many small antennas, and together they bend the beam toward the satellite. This is a phased array.

No motor means nothing to track mechanically. The beam steers electronically, so the dish can point at the next satellite without moving.

Handoff and the ground station

One satellite leaves and the next one picks up. That's the handoff, and it's what makes a moving constellation usable as a connection.

The satellite is still only a relay. The signal goes down to a ground station, where it moves from satellite to fibre. From there it joins the normal web.

So the full flow is the dish, then the satellite about 500 km up, then the ground station, then the internet.

What to take from it

If you get asked this in an interview, say it in three beats. Many small satellites at about 500 km instead of one big one. A phased array dish that steers its beam with no motor. A ground station that connects the satellite to fibre and the internet.

Then say what the answer is based on. It's the standard explanation and not Starlink's own internal design. That one line shows you know where your knowledge stops.

Send this to the friend who thinks Starlink is just dish TV. And if you have an opinion on Starlink versus Jio Fiber, that's a good thing to argue about in the comments.