This is imporant as I'm not sure I'd want to trust yet another service provider with my customers' data, especially one that is VC-backed and therefore inherently less trustworthy in the long-term than others.
For our users concerned about data locality, we recommend pushing the minimal data as arguments (ex: ids or external ids) and fetching the data during the execution on our side, if needed, through a dedicated SSH tunneling setup. Once an execution is done, its associated isolated container - gets a dedicated VPC and disk - gets destroyed permanently. We will also provide on-premises solutions for Enterprises.
In local environment (dev), background functions run completely synchronously and locally, no call is made to Defer.