Amazon, the world’s largest e-commerce retailer, has revealed it now employs 45,000 robots in some 20 fulfilment centres.

That’s a 50 percent increase from the same period last year when the company had some 30,000 robots working alongside 230,000 humans.

The e-commerce powerhouse has increased its robo-workforce by 15,000 a year over the past three years in concert with a big increase in human workers.

Its human workforce stood at 300,000 at the end of September last year.

The rapid growth in Amazon’s robot fleet showcases the company’s love for automation.

In 2012 the company bought Kiva Systems, a Boston-area robotics firm that invented the flat, toaster-like orange warehouse robots that now populate Amazon’s warehouses.

The Kiva mobile robot travels at a speed of 5.5km/h and can lift up to 340kg.

Amazon also employs other kinds of automata, such as arms that carry pallets.

Fine motor skills 

But most of the stowing and picking of items, which require fine motor skills and discernment, is done by human brains and hands – at least for now.

“We’ve changed, again, the automation, the size, the scale many times, and we continue to learn and grow there,” Amazon Chief Financial Officer Brian Olsavsky told the Seattle Times last year.

Mr Olsavsky said he couldn’t point to any “general trends” in the adoption of robotics, because some fulfilment centres are clearly “fully outfitted” in robots and “some don’t for economic reasons – maybe the volume’s not perfect for robot volume.”

Amazon’s experiments with automation extend well beyond the warehouse – into fields like artificial intelligence and computer vision, which have led the company to open a store without cashiers in Seattle. 

And in the UK, Amazon announced its first delivery via automated drone.