#Concurrency

How do you maintain database consistency, prevent double booking of seats, and manage seat inventory during high-concurrency booking scenarios?

Compare `ExecutorService`, `CompletableFuture`, and `Virtual Threads` (Project Loom) in Java. When would you choose one over the others?

Explain the Java Memory Model (JMM), the concept of happens-before relationships, memory visibility, and how `volatile` and synchronization work.

Explain how String immutability works in Java and how it contributes to thread safety.

Design a ConcurrentHashMap from scratch.