During the working week I suspend my desktop each evening. In the morning when I wake it I use the system authentication service (my login password) to unlock 1Password and there's a considerable lag time before the 1Password interface shows anything with a single 1Password process consuming lots of CPU (for about 20 seconds). This machine has a AMD 3900 processor so the CPU itself is not slow. The interface will just be a single solid grey colour until it is finally ready at which point the normal interface shows up and everything is snappy and responsive.
I cannot reproduce this by just suspending or putting it to sleep and immediately waking it which makes me think there's a time factor at play, like there's some part of the unlock process that's cached up to a point.
When this aspect isn't cached, it feels like each vault is being unlocked in turn single-threaded instead of one thread for each (but this is just an uninformed guess without seeing the code).