That sounds interesting. However, as soon as you have several distinct applications that share e.g. the same master data, how do do interface them? You will have to design the in-memory transactional store as a kind of global component. Then, not much is left until you end up with a real database.

I am working on a team that is building an in-memory SQL database. It features a custom language that makes it possible to push the time-critical, data-processing parts of the application directly to the database, which allows for the same speed as this no-DB approach. But you don't have to build your own DB and do everything yourself (correct persistence, backup, transactions...)