What would you use Redis for?

Could you elaborate on the potential use cases for Redis in the realm of cryptocurrency and finance? How might it enhance the performance and scalability of systems handling transactions, market data, or user authentication? Additionally, how does Redis's support for data structures like strings, lists, sets, sorted sets, and hashes contribute to its suitability for these applications? Lastly, are there any specific challenges or considerations that need to be addressed when integrating Redis into a cryptocurrency or financial system?