Java LLD: Designing a Thread-Safe Parking Lot with Strategy Pattern

Java LLD: Designing a Thread-Safe Parking Lot with Strategy Pattern

Designing a parking lot is a staple of Java LLD and machine coding interviews, yet most candidates fail to write production-grade code. As an ex-FAANG interviewer, I've seen countless designs fall apart under concurrent traffic or when asked to support multiple slot allocation algorithms.

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The Mistake Most Candidates Make

Monolithic locking on the entire ParkingLot class: Using a global synchronized keyword on the entry method, which serializes all gate entries and destroys system throughput.