Many of us don’t know our neighbors anymore — and Nirav Tolia wanted to change that. He walked away from millions in stock options at Yahoo and eventually co-founded Nextdoor, the hyperlocal social network where neighbors share local news and recommendations. Along the way, he learned that for a digital service, Nextdoor demanded a ton of manual work: drawing neighborhood boundaries with Sharpies, sending individual “invite” postcards by snail mail, talking to neighbors about the information they wanted. After 8 years of grind, Nirav stepped away as CEO, only to return 6 years later to spearhead an ambitious rebrand of Nextdoor, which now...