Select some live seafood in one of Alibaba's Hema grocery stores in Shanghai, get it rung up and bagged, and a robotic arm will whisk it away to a kitchen. Minutes later, a pod will wheel out of the kitchen, pulling up to your table with your meal under a transparent dome.

What's going on: A raised highway of robot pods has replaced human waitstaff in an already high-tech Hema — with humans mostly left to the greeting and cooking.

The big picture: Robot food runners may seem like a gimmick to get diners through the door. But if they become commonplace, it will be because high labor costs make them more cost-efficient than living, breathing waiters.

The context: In some cities around the world, waitstaff are expensive enough that they've been done away with, turning even nicer restaurants into Chipotle-style cafeterias where diners order at a counter, grab utensils, and bus their own table.

Some are going entirely robotic:

• JD.com, Alibaba's main e-c0mmerce competitor, says that next month, it will open a fully automated restaurant, staffed with no human cooks or servers, reports Daisuke Harashima of Nikkei Asian Review. By 2020, it will operate about 1,000 of them, JD says.
• The company — fiercely competing with Alibaba — has already taken the lead in commercial robotization with a wholly automated warehouse staffed with just four humans, all of whom service the robots.

But, but, but: In most cases, humans are still part of the equation. The automated Hema experience, for instance, still includes frail mortals welcoming customers, explaining the ordering system, taking payment, and — crucially — cooking the food.