Amazon’s decision to open its doors to outside sellers has been essential to its ability to get us almost anything in a matter of days, if not hours. It’s what lets us turn to it with the random, near stream-of-consciousness list of things that pop into our heads. Though my memory is hazy, I’m pretty sure one of my family’s first Prime Now orders came soon after my son was born: We got diapers, chocolate — and vermouth for Negronis.

Like Facebook in its effort to sort out fake news, Amazon has turned to algorithms to organize and police its site, and said it was spending $400 million a year to do so. On Thursday, the company said that it had record holiday sales and that “billions of items were ordered worldwide.”

Jeff Wilke, the chief executive of Amazon’s consumer business, told me that the company’s long-term future depended on patrolling the site without harming well-meaning merchants.

“We have a strong incentive to be as accurate as possible in identifying bad actors, make very few mistakes when we’re wrong,” he said, adding that Amazon also wants to give people second chances when they make an honest mistake.

People who have worked at Amazon’s marketplace debate whether the company can build systems fast enough, and accurate enough, to keep up. Some say the gap is closing; others fear the rot may grow too fast to catch.

I find myself thinking of a conversation I had toward the beginning of the year with Juozas Kaziukenas, founder of Marketplace Pulse, a research company. “If the chaos continues, I don’t know how long a consumer will be willing to put up with it,” he said. “They are a marketplace of trust, and if you cannot trust it, the whole premise of Amazon completely evaporates.”

That trust comes down to big decisions and little details, like those changes submitted five billion times a day.