For the last year, Google’s work force has increasingly been under attack from a herd of unicorns.

The unicorns, a class of hot start-ups valued at $1 billion or more, are all aggressively pursuing the best and brightest minds in Silicon Valley with promises of talked-about workplaces and eye-popping payouts. Amid a general scramble for talent, Google, the Internet search company, has undergone specific raids from unicorns for engineers who specialize in crucial technologies like mapping.

In particular, Uber — the largest unicorn, with a valuation of more than $50 billion — has plundered Google’s mapping unit over the last 12 months, aiming to bolster its own map research. Airbnb, the popular short-term rental start-up, has gone on a more general hiring spree, poaching more than 100 workers.

The recruiting is not confined to the best engineers; sometimes it spills over to nontechnical employees too. Two of the chefs who prepared meals for Googlers, Alvin San and Rafael Monfort, have been hired away by Uber and Airbnb in the last 18 months.

“It’s an employee’s market right now,” said Rodrigo Ipince, 28, a software engineer who recently left Google and was pursued by unicorns, but chose to join a mobile gaming video start-up, Kamcord. Mr. Ipince, who worked at Google for five years, said he received at least one to two emails from recruiters daily, asking if he was eager for a new job.

“It was fairly easy to get my foot in the door of whatever company I want,” he added.