Design the backend architecture for Spotify.

Focus on the key components that make up Spotify's backend architecture, such as data storage, user authentication, and streaming services. Consider how to handle large-scale data management for millions of users and tracks, including database choices (SQL vs. NoSQL) and caching strategies. Discuss the microservices architecture and how it can facilitate scalability and maintainability. Additionally, address how to ensure low latency for streaming and the importance of load balancing and redundancy in your design. Be prepared to explain your choices and how they contribute to a seamless user experience.