I'd love to see more advice regarding optimistic state and when it should be used. For Instagram or Facebook, it seems worth it to give them satisfaction even

I'd love to see more advice regarding optimistic state and when it should be used. For Instagram or Facebook, it seems worth it to give them satisfaction even while the request is processing - if they're lied to, it's not a big deal. In a financial app, this isn't the case. Anyone have any articles or resources about this? Is there ever a place for optimistic interfaces in financial or otherwise-serious apps?