Executive Summary: Asynchronous message queues, dead-letter exchanges, event sourcing, and idempotent message processing in distributed environments.

Event-driven architecture decouples producers from consumers using message brokers, ensuring high fault tolerance during service spikes. ### 1. Message Queue Guarantees - **At-Least-Once Delivery:** Consumers must be designed to be idempotent (processing the same message ID multiple times produces identical results). - **Dead Letter Exchanges (DLX):** Unprocessable messages (malformed JSON or database errors) are automatically moved to a DLX queue for developer inspection. ### 2. Kafka vs RabbitMQ Use Cases - **RabbitMQ:** Ideal for complex routing rules, priority queues, and task worker queues. - **Apache Kafka:** Ideal for high-throughput streaming log telemetry and event replay logs.