Physical tenant isolation is the strongest form of multi-tenant separation, where each tenant is given dedicated infrastructure — separate storage, compute, indexes, or even entire database instances — rather than sharing resources with other tenants. Nothing is pooled at the data layer, so tenants are isolated not just logically but physically.
This level of isolation is chosen when guarantees must be absolute. Because tenants share no resources, there is no possibility of data leaking between them and no noisy-neighbour effect where one tenant’s load slows another. Each tenant’s performance depends only on its own usage, and each can be secured, backed up, and scaled independently — qualities often required in regulated industries or for large enterprise customers.
The cost is efficiency. Dedicated resources per tenant multiply infrastructure and operational expense, which is impractical for applications with many small tenants. In practice, most vector databases provide physical isolation only through architectural patterns like dedicated shards, clusters, or databases per tenant, reserving it for those tenants that genuinely require it while serving the rest with lighter logical isolation.