Disclosed are various embodiments for allocating shared resources. A request to allocate a shared isolating resource is received. The shared isolating resource operates to isolate a plurality of customer resources in a multi-tenant environment. In response to the request to allocate, a least recently deallocated shared isolating resource is removed from a pool of available shared isolating resources. The least recently deallocated shared isolating resource is provided to at least one device using the shared isolating resource.