Jeff Bezos's main problem was the meat. In 2016, Amazon opened its first Go store, a till-free shop on the ground floor of its Seattle headquarters, which allowed customers to simply walk out and have their credit card automatically charged for the salads, energy bars or soft drinks they had taken off the shelves.
What the company did not say, according to Jon Reilly, a former Amazon executive who was involved in its planning, was that it was originally envisioned as a fully fledged grocery store that sold fresh food.
"Jeff nixed it, because his complaint was that people were going to be weird about meat," Reilly says. "He felt like walking out the door with just a piece of meat would be an odd thing to do. That was his friction point."
It was not the only time the world's most valuable retailer had seemed to have an identity crisis when it came to conquering the supermarket.
While Amazon has been selling groceries for more than a decade, and supermarket executives have long feared the company's ambitions, the tech giant has not seemed close to turning the food industry on its head in the same way that it has for books, CDs and electronics.
Online sales have remained a fraction of total grocery shopping and, within that fraction, Amazon has faced stiff competition.
Meanwhile, the jury is still out on the biggest acquisition in its 27-year history, 2017's US$13.4 billion (£9.5bn) acquisition of Whole Foods.
Sales at Amazon's physical stores, of which the upmarket grocer is the biggest part, declined in 2019 and 2020, and fell by 16 per cent in the first quarter of this year.
Despite a jump, most food shopping is done in-store
"I don't think anyone's happy with the progress they've made in grocery," says David Glick, a 20-year Amazon veteran and former logistics executive who left in 2018. "If you want to be the biggest retailer in the world, you have to be in grocery, but it's really freaking hard."
While Amazon often charges into a market quickly, blindsiding incumbents, its progress in the food business has been the opposite.
In 2007, the company first started inviting users to test food deliveries in Seattle (originally, the Amazon Fresh programme was designed for employees, some believed in order to let them spend longer at work).
It was not until six years later that it moved out of the company's hometown, and it took until 2016 to move out of the US, arriving in parts of London.
Since then, it has had an often confusing array of other services: Pantry, for selling shelf-based staples like shampoo, crisps and water; Prime Now, for household essentials in under two hours; Go, the physical stores that use cameras to detect what shoppers have picked up; and Fresh Pickup, which lets shoppers collect orders at special sites.
In the UK, it has begun selling food from Morrisons. The Whole Foods purchase was the most audacious swoop yet, sending shock waves through the supermarkets.
"It's been a real spray and pray approach," says Sanchit Jain, an e-commerce analyst at Enders Analysis. "Those offerings have basically been trying to replicate the CD and books model for groceries. I think what Amazon overestimated was the consumer appetite for actually purchasing their weekly shop online."
Online groceries have been a slow burner.
In Britain, the world's most enthusiastic market, the internet accounted for less than 10 per cent of grocery spending little more than a year ago.
That changed during the pandemic, with deliveries as a percentage of total grocery spending doubling year on year. Amazon said its own online grocery sales saw similar growth towards the end of last year.
But the company does not dominate online grocery shopping. Some market researchers say that Amazon was surpassed by Walmart as America's biggest online grocer last year.
In the UK, the company has just a three per cent share of online sales, compared to 14 per cent for Ocado and over 30 per cent for Tesco, according to Mintel.
Glick says the company has found its logistics expertise did not transfer to perishable items without a huge network of its own stores.
"If you are ordering from Amazon proper, it's a big million square foot building, and no customers in the store screwing up your inventory. When you go into grocery stores you're going to have to replicate your inventory into 1,000 different stores. That takes away the advantage."
A former British grocery executive argues that while Amazon's website is fine tuned to deliver instant results, most shoppers use it only to buy one or two items at a time.
Buying dozens of items online at once, by comparison, feels time consuming - often more so than travelling to a supermarket. And for British shoppers that still remember the horse meat scandal that plagued supermarkets in the UK, buying certain perishables on the internet, especially from new players, can feel uncertain.
"This is stuff that the customer has to have an intense trust about; it's the reason Ocado had to start with Waitrose," the executive says. "I think they had a kind of certain naivety that the fact that they were Amazon was going to make up for that."
Reilly says that Amazon's wooing of Chinese sellers in the last decade, which has boosted sales but led to multiple safety questions, may have also made some consumers reluctant. "Amazon overestimated the amount of trust that consumers have in them," he says.
The company's answer has been a bigger bricks and mortar presence.
In 2019, it opened its first Amazon-branded Fresh supermarket near Los Angeles. Like the smaller Go stores, it uses computer vision to identify items placed in trolleys, letting shoppers skip the tills on the way out. It now has a dozen Fresh supermarkets in the US and four smaller ones in the UK.
Bezos is relying on this being enough of a draw to convince shoppers to switch from grocers they may have used for decades.
"Once you try it, you'll love it. It's delightful," he told a shareholder at last week's annual meeting. "Grocery is one of our fastest growing categories, and it continues to be a big priority for Amazon," he said.
Stores are expected to dominate grocery shopping, even after the boost that online sales received during the pandemic. Amazon may have finally acknowledged that.
"Maybe the answer is that customers like to go to stores. And so they're starting with that," says Glick.
The effort the company is putting into building its own store network, even if it is the right decision, appears to jar with the fact that the company spent billions buying Whole Foods, which has more than 500 stores across the US, Canada and UK.
As Bezos prepares to step down as chief executive in July, and after last week's news that Amazon is paying almost US$9b for Hollywood studio MGM, his biggest deal remains a rare question mark on the billionaire's CV.
That does not, however, give much cheer to supermarket bosses, who still fear the company could one day decide to swoop on a big UK grocer.
"They would take the world over" says one executive. "Amazon with a physical footprint in the UK of that scale would be quite frightening."