Explain advanced distributed locking mechanisms and consistency trade-offs in PHP systems.

Distributed locking coordinates access to shared resources across multiple nodes, but introduces trade-offs between consistency, availability, and performance.

Distributed locking is required when multiple PHP services or workers need exclusive access to a shared resource (e.g., inventory updates, scheduled jobs, or financial transactions).

Unlike in-process locks, distributed locks must handle:

Common implementations:

SET key value NX PX ttl

SELECT ... FOR UPDATE

Consensus-based coordination

Redis cluster-based lock proposal (controversial under certain failure assumptions)

Core risks:…