For SaaS products, high availability is the foundation of your customers trust. Releasing a constant flow of new features is what differentiates you in the market. Combining the two - maintaining a robust yet continuously-evolving service - is very challenging. We’ve had the same challenge at Twilio. We will share what we learnt and the technical choices we took in different parts of our architecture. We will also show how to apply those patterns to build voice use cases with high availability.