Today, it’s pretty normal to write new applications in a “cloud-native” way. Whether we deliver to a public cloud or use a container fabric behind the firewall, we commonly work with microservices or serverless. A data store is as likely to be block storage or Mongo as it is a traditional database. This makes sense. Small components match well with DevOps teams operating independently (see Conway). In general, modern architecture, infrastructure, and delivery approaches support more frequent releases and more resiliency in production. All good things.
However, most apps are not new. A typical enterprise can have many hundreds to a couple of thousand existing applications. Do they sit as they are until replaced? Do we rearchitect them all? Will some move? And if so, which?