Design Satellite Imagery Platform - System Design | WinJob

Earth observation platform framing and capture lifecycle

Numbers to state early

Metric A: 200 EO satellites
Metric B: 3 m GSD
Metric C: daily revisit

Mechanism

Planet-style daily global coverage starts with constellation tasking: each satellite schedules nadir or off-nadir captures based on cloud forecasts and customer AOIs. Raw downlink hits ground stations, then ingest validates checksums, attaches orbit metadata, and enqueues L1 radiometric correction before any user sees a tile.

Failure and edge cases

If Downlink saturates during a pass, prioritize paid SLA AOIs and defer opportunistic captures. Partial files must land in quarantine with capture_id so reprocessing does not double-bill customers.

Open with capture → correct → tile → analyze—interviewers confuse imagery platforms with photo CDNs. Name ground resolution (GSD) and revisit cadence before drawing boxes.

Java

javaOne Dark Pro

1 public final class ImageryCtx1 {
2   private final String captureId;
3   private final long epochMs;
4  
5   public ImageryCtx1(String captureId, long epochMs) {
6     if (captureId == null || captureId.isBlank()) throw new IllegalArgumentException("id required");
7     this.captureId = captureId;
8     this.epochMs = epochMs;
9   }
10  
11   public String partitionKey() {
12     return captureId + ":" + (epochMs / 86_400_000L);
13   }
14 }

Python

pythonOne Dark Pro

1 from dataclasses import dataclass
2  
3 @dataclass(frozen=True)
4 class ImageryCtx1:
5     captureId: str
6     epoch_ms: int
7  
8     def partition_key(self) -> str:
9         if not self.captureId:
10             raise ValueError("id required")
11         return f"{self.captureId}:{self.epoch_ms // 86_400_000}"

TypeScript

typescriptOne Dark Pro

1 export interface ImageryCtx1 {
2   captureId: string;
3   epochMs: number;
4 }
5  
6 export function partitionKey(key: ImageryCtx1): string {
7   if (!key.captureId) throw new Error("id required");
8   return `${key.captureId}:${Math.floor(key.epochMs / 86_400_000)}`;
9 }

Why interviewers care

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

Interview checkpoint

Name one failure story for Earth observation platform framing and capture lifecycle that proves you understand real outages, not happy-path diagrams.

Key Highlights

•200 EO satellites
•Constellation → Downlink → Ingest
•Planet-style **daily global coverage** starts with **constellation tasking**: ea

1	public final class ImageryCtx1 {
2	private final String captureId;
3	private final long epochMs;
4
5	public ImageryCtx1(String captureId, long epochMs) {
6	if (captureId == null \|\| captureId.isBlank()) throw new IllegalArgumentException("id required");
7	this.captureId = captureId;
8	this.epochMs = epochMs;
9	}
10
11	public String partitionKey() {
12	return captureId + ":" + (epochMs / 86_400_000L);
13	}
14	}

1	from dataclasses import dataclass
2
3	@dataclass(frozen=True)
4	class ImageryCtx1:
5	captureId: str
6	epoch_ms: int
7
8	def partition_key(self) -> str:
9	if not self.captureId:
10	raise ValueError("id required")
11	return f"{self.captureId}:{self.epoch_ms // 86_400_000}"

1	export interface ImageryCtx1 {
2	captureId: string;
3	epochMs: number;
4	}
5
6	export function partitionKey(key: ImageryCtx1): string {
7	if (!key.captureId) throw new Error("id required");
8	return `${key.captureId}:${Math.floor(key.epochMs / 86_400_000)}`;
9	}