Reduce memory overhead of _deserialize_from_store

[bjester]

Observed behavior

When syncing large amounts of data and upon successful transfer, that data is deserialized into the store (_deserialize_from_store), memory usage often spikes.

Expected behavior

The behavior of _deserialize_from_store should reduce its memory usage by loading only the necessary data / models into memory.

User-facing consequences

In some online deployments with strict resource constraints, OOM killer may kill the process that is handling the deserialization.