> its a system design issue or system availability issue on the client side

If all events need to arrive, then the problem is not "notification" (which would be solved by webhooks) but "database replication": subscribe to new events, fetch the full snapshot, fetch the updates in range, have the monotonic value to establish the "range" in the first place. Reach the eventual consistency.

The proposed SCROLL handles half of these, which limits its use-cases.