When did you last spend time optimizing that sluggish part of your product? You know the one I'm talking about — the one that everybody hates testing because it takes so long, where you have to sit and watch the spinner for many seconds, wondering whether we've really come as far as we think we have since Windows XP. Has it really been that long since anyone took a look at it and tried to figure out why it's so slow?
If you really truly don't have time today, come back to this post tomorrow. Bt if you do — even a spare half hour between meetings — you should spend some time going through the code of that sluggish feature. You don't have to fix it today, but get an idea of how it works, so that your subconscious can chew on the problem while you sleep. Or, if you have lots of time, maybe you can fix it today — it's probaby more obvious than you think, once you dig deep enough.
Remember, if you think this feature is slow on your turbocharged dev machine, your users definitely think it's slow. They've come up with strategies for avoiding that feature already, if they haven't jumped ship for a competitor. Nobody has time to sit around watching a spinner turn these days.
So: even if it's not on Trello, even if your PM doesn't think it's a priority, find a bit of spare time and take a look. It can't hurt, and everyone will thank you once it's fixed.