Psst! Wanna buy a unicorn?

Hi, everyone. It's Shira. Later today, Lyft Inc. will likely sell its first batch of stock as a public company. It's a milestone for ride-hailing company, and it will officially kick off the great tech unicorn IPO barrage of 2019.

Depending on your perspective, this flood is either validation for the class of companies created since smartphones and cloud computing made new technology businesses possible, or a sign that startups are rushing to catch the last innings of the decade-long U.S. stock market expansion.