How we use formal modeling, lightweight simulations, and chaos testing to design reliable distributed systems

The text discusses the challenges of designing and testing distributed systems due to their increased complexity and failure modes. It highlights the use of formal modeling and lightweight simulations as techniques for verifying system behavior at any desired level of abstraction, tracking it from concept to sometimes even code. The author shares insights gained while working on a new message queuing service named Courier using these approaches. They also discuss the limitations of these methods and the importance of keeping models and simulations up-to-date with the design of a system. Finally, they mention the potential use of deterministic simulations for testing distributed systems in the future.