What network does Kraken use?

Could you elaborate on the underlying network that Kraken utilizes for its cryptocurrency transactions and financial services? As a professional in the field of cryptocurrency and finance, I'm curious to understand the technological backbone that drives this platform. Is it a public blockchain, a private blockchain, or a hybrid approach? Additionally, how does this network ensure the security, scalability, and overall efficiency of Kraken's operations? Your insights into this matter would be greatly appreciated.