Well yes and no if you had enough resources imaging something like Spanner but highly optimised for multi-tenancy. There will be higher latency because inactive

Well yes and no if you had enough resources imaging something like Spanner but highly optimised for multi-tenancy. There will be higher latency because inactive tenant's data got purged from caches but it would be nowhere near the latency of spining up a postgres instance. You could even have a smart stats layer that tracks usage and keeps some minimal amount of inactive tenants data in memory to minimize latency.