Out-of-Order Events and Duplicate Processing in Microservices: Hard Lessons in Verification Tooling and the PEP 668 Wall
Out-of-Order Events and Duplicate Processing in Microservices: Hard Lessons in Verification Tooling and the PEP 668 Wall 1. Context & Architectural Overview In distributed event-driven microservices architectures, ensuring message ordering and idempotency is a classical challenge. When services communicate asynchronously via brokers (e.g., Apache Kafka, RabbitMQ, or AWS SQS/SNS), network partitions, worker scaling, and consumer retries inevitably introduce out-of-order deliveries and duplicate…