The cloud is great for elasticity, so in scenarios where compute or storage demands can surge extremely and unexpectedly/at short notice, that is core "cloud te

The cloud is great for elasticity, so in scenarios where compute or storage demands can surge extremely and unexpectedly/at short notice, that is core "cloud territory". When you have reliability/continuity as a top business requirement and ACID transactions (e.g. billing) must be processed at scale, then mainframes shine. The argument "Never change a running system." is not a wrong one, but it does not on its own explain the existence of mainframes; there are non-legacy scenarios where using a mainframe is the most reasonably choice. Finally, "cloud" as a term denoting outsourced compute/storage capacity can also apply to mainframes, see e.g. IBM's pricing brief at https://www.ibm.com/downloads/cas/YM94KV6N https://www.ibm.com/downloads/cas/YM94KV6N - some own their mainframe, some rent it - like a prive or public (internal or external) cloud.