[AdieuToLogic]

> A concrete example would be a users shopping cart, as they build it. You don’t need the niceties of a fully ACID compliant DB, you need write performance, and extremely high availability.

Using a key-value store for shopping carts can work for awhile, especially for the use-case you describe, but fails when system functionality grows beyond retrieving only by a cart ID.

And when using a persistent store which does not provide ACID capabilities, the system will ultimately have to enforce at least atomicity and consistency via server logic.

[makeitdouble]

> when system functionality grows beyond retrieving only by a cart ID.

Either you manage your system so it never ever uses any other key than a cart ID (services have been running for decades keeping the same unique ID, that's not some unreasonable thing).

Or you migrate your data to match the completely wild new requirement, and taking costly steps to deal with a funfamental business change would be seen as reasonable in most orgs.