You have 30 days to respond to a data request, so the default GDPR behavior is to delete all data within 30 days. You also mostly want stat-significant aggrega

You have 30 days to respond to a data request, so the default GDPR behavior is to delete all data within 30 days. You also mostly want stat-significant aggregations, so if you take care to keep those differentially private (only aggregate large groups etc.) you can keep that data. Just make data persistence opt-in rather than opt-out, eg delete all old files by default.