To answer these questions for you: mainframes are perfect for transactional workflows. Wait but you haven't told me what a transaction is!!! So... by a transac

To answer these questions for you: mainframes are perfect for transactional workflows. Wait but you haven't told me what a transaction is!!! So... by a transactional workflow, typically it's going to be some workflow where you get a request, perform some operations on a database, and then sometimes return a response. This can be a withdrawal from an ATM, a trade received by a broker, a new user registering on a website, etc. Mainframes have CPUs and hardware designed to accelerate and make these transactions more robust over commodity hardware. An example is with hardware compression and robust transactional memory when using DB2. It's not uncommon to see mainframes with decades of uptime. You just don't get that with commodity hardware. Mainframes are cheap when you really do have simple transactional workflows like this at massive scale. Financial institutions are an obvious choice as a result. Since they're so reliable and you're dealing with a simple node, the cost savings can be significant.