Over the summer, Amazon converted most of the 175,000 contract workers to permanent employees and ended the additional raise for all workers. Since then, it has continued with waves of attitudes.
The company has also nearly tripled the number of U.S. warehouses used for last mile deliveries this year, said Marc Wulfraat, founder of logistics consultancy MWPVL International, which tracks Amazon's operations. The delivery drivers are usually contractual partners, so Amazon does not include their numbers in official documents.
"They have built their own UPS in the past few years," said Wulfraat. "This rate of change has never been seen before."
Ms. Williams said Amazon has also built relationships with downsizing companies like Uber, American Airlines and Marriott to encourage recruitment.
"We hired a group that did nothing but affiliate with organizations that took people off, be it temporary or permanent," she said. "This enabled us to hire qualified, high-quality workers and quickly and easily convert them into opportunities that were appropriate at Amazon."
The effort was supported by 1,000 technology workers who create software for Amazon's human resources department. Many are building portals and algorithms that automate the hiring process, she said. Potential employees can find jobs, apply and be hired entirely online without speaking to a single person.
In order to grow so strongly, Amazon must also think long-term, said Ms. Williams. As a result, the company has already worked with preschools to lay the groundwork for technical training. "As our hiring demand unfolds over the next 10 years, this pipeline is there and ready."
Michael Corkery contributed to the coverage from New York.