What if I use postgres with a large dataset would this setup perform better than keto or opa? OPA has a pull data during evaluation feature (https://www.openpolicyagent.org/docs/latest/external-data/#option-5-pull-data-during-evaluation) which might be similar to how spicedb works. Apart from some complexity, are there any drawbacks of using this feature instead of spicedb for building an authorization server?