Design a Distributed Message Queue

Designing a distributed message queue involves several key considerations:

1. Core Concepts: Understand different messaging patterns like point-to-point, publish-subscribe, and fan-out/fan-in. Acknowledge the complexity and nuances of distributed systems.
2. System Design: Discuss requirements gathering (e.g., throughput, latency, durability) and relevant metrics. Consider storage mechanisms, such as Write-Ahead Logging (WAL), for durability and recovery.
3. Distributed Challenges: Address critical aspects like message guarantees (at-least-once, at-most-once, exactly-once), message ordering across distributed nodes, replication strategies for fault tolerance, and architectural choices (e.g., master-slave, leader-follower, or fully distributed consensus).
4. Scalability & Availability: Plan for horizontal scaling to handle increasing load and ensure high availability through redundancy and failover mechanisms.