Explore the challenges of scaling an Appointment Reminder system from a simple concept to a robust solution serving millions of patients weekly in this 18-minute conference talk from RubyConf 2021. Discover the journey of a development team as they navigate performance issues and increasing complexity, leading to four complete rewrites of their main product. Gain insights into solving seemingly trivial problems that become complex at scale, and learn valuable lessons about system design and optimization. Delve into the team's experiences, strategies, and key takeaways as they share their process of creating the perfect design for a high-volume messaging system.