While browsing one day, Emma clicked a link on a site and nothing happened. That was annoying, but Emma wasn't about to give up. She tried to get the URL out of the link, only to discover that there wasn't a URL. Or a link. A quick trip to the DOM inspector highlighted what was going on:

<div id="I32" align="left" onclick="ItemClick(3,2)" 
onmouseout="RollOut(3,2,false)" 
onmouseover="RollOver(3,2,false)" 
style="position: absolute; top: 43px; left: 1px; width: 176px; height: 16px; font: bold 8pt Arial; color: rgb(1, 35, 69); background: none repeat scroll 0% 0% rgb(255, 255, 255); padding: 2px; cursor: pointer; border: 0px solid rgb(255, 255, 255);">Project Office</div>

NoSQL databases frequently are designed to shard or partition across many nodes. That, of course, makes enforcing unique IDs different than you might do in a SQL database. You can't efficiently have an autoincrement sequence, and instead have to have something like a UUID.

But if you've designed your NoSQL database badly, or your input data isn't well sanitized, you might find yourself in a situation where you can't guarantee uniqueness without validating every row. That's a bad place to be, but it's probably how the code Remco found started its life.

David was poking around in some code for a visualization library his team uses. It's a pretty potent tool, with good code quality. While skimming the code, though, David found this mismatched comment and code:

    def get_tip(self):
        # Returns the position of the seventh point in the path, which is the tip.
        if config["renderer"] == "opengl":
            return self.points[34]

        return self.points[28]  # = 7*4

Michael was assigned a short, investigatory ticket. You see, their PHP application allowed file uploads. They had a rule: the files should never be larger than 20MB. But someone had uploaded files which were larger. Not much larger, but larger. Michael was tasked with figuring out what was wrong.

Given that the error was less than half a megabyte, Michael had a pretty good guess about why this was.