How would you design a scalable and fault-tolerant e-commerce system that can handle millions of transactions per day? Design a distributed cache system like Redis to improve the performance and scalability of a web application. Discuss the architecture and design considerations for a recommendation system that suggests personalized content to users based on their preferences. Design a scalable and highly available video streaming platform like YouTube, considering aspects such as video storage, content delivery, and handling concurrent viewers. How would you design a ticket reservation system for a large event venue, ensuring seat availability, transaction consistency, and optimal user experience? Design a distributed file storage system that allows users to store and retrieve files securely and efficiently across multiple servers.