Delivery Guarantees in Messaging Systems

This post explains the concepts of at-most-once, at-least-once, and exactly-once (effectively once) delivery guarantees in messaging systems. It uses the Two Generals Problem as an analogy to illustrate the challenges of achieving reliable communication over unreliable networks. The post discusses the implications of each delivery guarantee, drawing parallels to science fiction teleportation scenarios. It concludes by relating these concepts to modern software development, especially in distributed systems and financial transactions, and mentions Apache Kafka's transactional guarantees as a solution.