You don’t have to be in the retail to know what a big deal Black Friday is. The promotions for sales the day after the U.S. Thanksgiving holiday are everywhere, from billboards to online. The Balance, a personal finance content website points out that Black Friday is one of the biggest and most profitable retail days of the year. And the phenomenon extends far beyond the U.S.: Bustle.com reports that nearly 20 different countries have Black Friday sales of their own. But what if a retail company faced the prospect of its core digital systems being down during this pivotal four days? Building o…