The first outage on June 20 was an internal glitch with the retailer's delivery processing system, forcing the chain to take down its site because it couldn't fulfill the orders. But the site itself wasn't the problem.
On July 4, it was the opposite: The supply chain systems were operating but the site itself—specifically, the homepage—was crashing for about an hour before a temporary homepage was put up, according to Sainsbury's spokesperson Gillian Taylor.
Because the Sainsbury's homepage is hosted by a different company than the rest of the site, everything else, including online grocery shopping, worked fine during the outage. The temporary page was live for 24-hours until the normal homepage was back up.
Taylor would not say what caused the homepage to crash, but added that it was completely unrelated to the June outage.
"It wasn't the same kind of issues we had last time," Taylor said. "We put up a temporary homepage, so customers could still continue to shop."
That June crash was caused by an unrelated processing problem. It froze the delivery services for Sainsbury's, preventing customers from shopping online for about 48 hours. That glitch prevented about 30,000 customers from getting their groceries and prompted Sainsbury's to issue almost a half a million dollars worth of vouchers to those disgruntled shoppers.
The chain also personally called each of those 30,000 affected customers and explained to them what happened.
During that meltdown, U.K. grocery competitors took advantage of Sainsbury's problem, according to a June 21 article in The Grocer. U.K. retailer Ocado saw a surge in orders and offered new customers a 15 percent discount, while Asda, another competitor, placed a sponsored link on Sainsbury's Google searches offering free deliveries.