Design a file cache system.

Focus on the key components of a file cache system, including how to store, retrieve, and invalidate cached files. Consider the types of files being cached and the expected access patterns—will it be read-heavy or write-heavy? Discuss the caching strategies you might employ, such as Least Recently Used (LRU) or time-based expiration. Address scalability and performance, and think about how to handle cache misses and synchronization in a multi-threaded environment. Finally, be prepared to explain your design choices and trade-offs clearly.