That's assuming that you're actually picked for a jury. I've been called for jury duty ... I dunno, well over a dozen times, I've gone through voir dire 3-4 times, and I've been eliminated each time (which sucks, 'cause I think it'd be interesting, but whatever).

Your courts may operate differently, but my experience across multiple states has been: I'm summoned for a week of jury duty. I show up on Monday and am assigned to a pool. We sit around for a while. About 2/3's of the time we're eventually just sent home, with instructions to call a certain number every evening that week. The number will tell us if we're needed the following day, but I've never had to return to the courthouse during the week.

The other third of the time, we get called for the selection process. They go through the pool until they have enough people for the jury+alternates. I think I've only been through selection 2 or 3 times, and I've always been eliminated.

If it were me, I'd show up for the first court on Monday. If you don't get selected, NBD and you can go through selection again for the other court on Wednesday. If you do get selected, you can then contact the second court, explain that you're currently serving on a jury, have your first court send over whatever paperwork is required, and defer your service with the second court. But you have a decent shot at getting through the week without serving at all, after which you'll be removed from those potential jury pools for a few years.