Offline Snap-store for juju-db installation

Team, I am trying juju bootstrap with apt-mirror on air-gapped environment. Juju agent is served with simplestream but still juju-db expects

Is snap-store-proxy only option for private snap-store?

Is there any other workaround to install juju-db offline.

Please help me. Thank you.

2023-08-25 01:19:00 INFO juju.packaging.manager run.go:88 Running: snap install  --channel 4.4/stable juju-db
2023-08-25 01:19:00 ERROR juju.packaging.manager run.go:144 packaging command failed: exit status 1; cmd: "snap install  --channel 4.4/stable juju-db"; output: error: cannot install "juju-db": Post Internal Server Error