During this configuration change, a traffic shift "was executed incorrectly," Amazon said, noting that traffic that should have gone to a primary network was routed to a lower capacity one instead. The error occurred at 12:47 p.m. on April 21 and led to a partial outage that lingered through last weekend.

The outage sent a number of prominent Web sites offline, including Quora, Foursquare and Reddit, and renewed an industry-wide debate over the .

Amazon posted updates, short and bulletin-like, throughout the outage, but what it offered in is entirely different. This nearly 5,700-word document includes a detailed look at what happened, an apology, a credit to affected customers, as well a commitment to improve its customer communications.

Amazon didn't say explicitly whether it was human error that touched off the event, but hints at that possibility when it wrote that "we will audit our change process and increase the automation to prevent this mistake from happening in the future."

The initial mistake, followed by the subsequent increase in network load, exposed a cascading series of issues, including a "re-mirroring storm" with systems continuously searching for a storage space.