In terms of GDPR compliance the fundamental element is pseudonymization of internal dataflows and data management -- that'll work with any data store. I mean,

In terms of GDPR compliance the fundamental element is pseudonymization of internal dataflows and data management -- that'll work with any data store. I mean, there is some possible advantage by having all users in their own actor-namespace, for bulk deletes and concrete mapping of data-usage, but IME you're always stuck with a need to preserve the operational state of the application and the quality of its legacy data. Regardless of sharding strategy, somehow your datawarehouse needs to be able to pull out or confirm data from the previous quarter...