Design Smart Parking System - System Design | WinJob

Problem Statement: Urban Parking Discovery

Design Smart Parking Platform (SpotHero / ParkMobile / REEF-class discovery) for urban drivers and parking operators. This section covers problem statement: urban parking discovery in the understanding phase.

Operational detail

Partition by facility_id and city_id so one operator cannot saturate shared ingest. State AP for live occupancy (stale pins greyed) and CP for holds and payment capture. Quantify search and ingest before naming cloud SKUs.

Failure and edge cases

Sensor flapping shows 0 then 1 spots; event surge sells out inventory twice; operator API outage blanks a garage row.

Interview checkpoints

javaOne Dark Pro

1 public record FacilityId(String value) { } // sec-01 parking boundary

pythonOne Dark Pro

1 def is_hold_expired(expires_at_epoch: float, now_epoch: float) -> bool:
2     return now_epoch >= expires_at_epoch  # sec-01

typescriptOne Dark Pro

1 export function stalenessMs(observedAt: number, now: number): number {
2   return now - observedAt;  // sec-01
3 }

Why interviewers care

Smart Parking System interviews reward crisp scope, explicit trade-offs, and failure stories—not generic microservice diagrams.

Interview checkpoint

Name one failure story for Problem Statement: Urban Parking Discovery that proves you understand real outages, not happy-path diagrams.

Key Highlights

•Drivers search by destination + arrival window, not arbitrary coordinates only
•SpotHero-scale: millions of monthly bookings; downtown cores see 50K concurrent map viewers
•Inventory spans garages, surface lots, private driveways, and metered street segments
•Occupancy truth mixes IoT loops, LPR cameras, gate counters, and operator CSV feeds

1	def is_hold_expired(expires_at_epoch: float, now_epoch: float) -> bool:
2	return now_epoch >= expires_at_epoch # sec-01

1	export function stalenessMs(observedAt: number, now: number): number {
2	return now - observedAt; // sec-01
3	}