[flurie]

This was true when it was first released, but they now allow you to bring your own backend store.

https://www.pulumi.com/docs/intro/concepts/state/

[edaemon]

That page lists this as a feature of their service, implying it isn't available in other backend stores:

Concurrent state locking to prevent corrupting your infrastructure state in a team environment

[terrorbilly]

It's specifically the state-locking feature that's missing from 3rd party backends.