Fair enough—there was some type of upgrade, techs encountered unexpected problems and the job of getting everything working again far outlasted the scheduled maintenance window. That makes perfect sense, until you think about it for a moment. After all, why would Walgreens schedule an upgrade for a busy time like Monday afternoon? That's the sort of thing you do in the middle of the night over the weekend. And that's probably what Walgreens actually did.
Consider: If the maintenance window was scheduled over the weekend, there should have been plenty of time for an installation or upgrade, and even some spare room in the schedule for things to go a little awry. But if things go seriously wrong, there's no such thing as a big enough maintenance window. A major problem would have meant a scramble in the data center to get the site back up and limping along well enough to make it through Monday.
If that's what happened, it almost worked. The site just didn't quite make it all the way to the late-Monday-night maintenance window.
Or maybe the new release was completed on schedule and appeared to work fine until Monday afternoon—and then something went unexpectedly wrong. Or perhaps the Web site admins started seeing problems early in the day and gambled that they could keep things going—and lost that bet.
Walgreens wouldn't elaborate, so we don't know the details. Then again, just getting that much explanation from the usually tight-lipped Walgreens is a pleasant change. It wasn't a denial-of-service attack or a catastrophic POS collapse or a complete E-Commerce meltdown—just another reminder that any Web site upgrade can go wrong in a very public way.