Java Concurrency LLD: Build a Custom BlockingQueue From Scratch At Apple and Amazon, implementing a thread-safe BlockingQueue is one of the most frequent concurrency challenges in Low-Level Design (LLD) interviews. It immediately exposes whether you understand thread coordination, thread-safe state mutation, and JVM internals, or merely rely on off-the-shelf utilities. The Mistake Most Candidates Make Relying on intrinsic locks ( synchronized ) with notifyAll() , which t...