Design Satellite Internet - System Design | WinJob

LEO broadband problem framing and constellation lifecycle

Global IP connectivity from a low-Earth-orbit shell: user terminals, moving satellites, ground gateways, and optional inter-satellite laser links form a mobile network in the sky.

Numbers to state early

Metric A: 6,000 LEO sats
Metric B: 25–45 ms RTT
Metric C: 550 km shell

Mechanism

Packets leave a phased-array user terminal, uplink to whichever satellite is visible, then ride ISL hops or bent-pipe RF to a ground gateway that peers with terrestrial ISPs. Orbital mechanics mean every cell is a moving hotspot—routing must be predictive, not static DNS.

Failure and edge cases

Rain fade on Ka-band can drop SNR 10 dB in minutes; the control plane must re-point beams and pre-stage handoff before TCP RTOs fire. A dead satellite is a moving outage—traffic shifts via ISL graph recalculation within seconds.

Open with moving topology: unlike fiber POPs, your routers orbit at 7.5 km/s. Interviewers want you to name gateway backhaul as the terrestrial choke point.

Java

javaOne Dark Pro

1 public final class OrbitalCellId {
2   private final String orbitalShellId;
3   private final long epochMs;
4  
5   public OrbitalCellId(String orbitalShellId, long epochMs) {
6     if (orbitalShellId == null || orbitalShellId.isBlank()) throw new IllegalArgumentException("shell required");
7     this.orbitalShellId = orbitalShellId;
8     this.epochMs = epochMs;
9   }
10  
11   public String partitionKey() {
12     return orbitalShellId + ":" + (epochMs / 60_000L);
13   }
14 }

Python

pythonOne Dark Pro

1 from dataclasses import dataclass
2  
3 @dataclass(frozen=True)
4 class OrbitalCellId:
5     orbital_shell_id: str
6     epoch_ms: int
7  
8     def partition_key(self) -> str:
9         if not self.orbital_shell_id:
10             raise ValueError("shell required")
11         return f"{self.orbital_shell_id}:{self.epoch_ms // 60_000}"

TypeScript

typescriptOne Dark Pro

1 export interface OrbitalCellId {
2   orbitalShellId: string;
3   epochMs: number;
4 }
5  
6 export function partitionKey(key: OrbitalCellId): string {
7   if (!key.orbitalShellId) throw new Error("shell required");
8   return `${key.orbitalShellId}:${Math.floor(key.epochMs / 60_000)}`;
9 }

Why interviewers care

Satellite Internet interviews reward crisp scope, explicit trade-offs, and failure stories—not generic microservice diagrams.

Interview checkpoint

Name one failure story for LEO broadband problem framing and constellation lifecycle that proves you understand real outages, not happy-path diagrams.

Key Highlights

•6,000 LEO sats
•Terminal → LEO Sat → Gateway
•Global IP connectivity from a low-Earth-orbit shell: user terminals, moving satellites, ground gatew

1	public final class OrbitalCellId {
2	private final String orbitalShellId;
3	private final long epochMs;
4
5	public OrbitalCellId(String orbitalShellId, long epochMs) {
6	if (orbitalShellId == null \|\| orbitalShellId.isBlank()) throw new IllegalArgumentException("shell required");
7	this.orbitalShellId = orbitalShellId;
8	this.epochMs = epochMs;
9	}
10
11	public String partitionKey() {
12	return orbitalShellId + ":" + (epochMs / 60_000L);
13	}
14	}

1	from dataclasses import dataclass
2
3	@dataclass(frozen=True)
4	class OrbitalCellId:
5	orbital_shell_id: str
6	epoch_ms: int
7
8	def partition_key(self) -> str:
9	if not self.orbital_shell_id:
10	raise ValueError("shell required")
11	return f"{self.orbital_shell_id}:{self.epoch_ms // 60_000}"

1	export interface OrbitalCellId {
2	orbitalShellId: string;
3	epochMs: number;
4	}
5
6	export function partitionKey(key: OrbitalCellId): string {
7	if (!key.orbitalShellId) throw new Error("shell required");
8	return `${key.orbitalShellId}:${Math.floor(key.epochMs / 60_000)}`;
9	}