[lolinder]

The biggest question to ask yourself is what are the failure modes you're worried about?

Redux isn't going to suddenly go offline, because it's running in the same process as your UI code. Redundancy therefore buys you nothing. The important failure modes in single-process UI code are all logic errors, and the best defense against those is to reduce the amount of unnecessary logic: so use a single source of truth.

With a database, the failure modes are very different. You're using a battle-hardened database whose logical consistency you have every reason to trust. The biggest failure modes are driven by the fact that you're running on a network, and networks are flaky. The best mitigation against these failures is to run redundant copies and trust that the database authors got their syncing code right.