Major tech companies (e.g. Netflix, Cloudflare, MongoDB, and nearly every other publicly listed high growth tech company) have seen their stock prices fall as much as 50% in the past few months.

When the value of the entire tech industry shrinks that dramatically this quickly, companies are bound to become a bit more conservative in their operations, which cloud slow the pace of hiring in tech (and for some, layoffs)

As for "when", the slow down has already started and will accelerate over the next few months (my prediction, no evidence).