When Erik Cassel and I launched the precursor of our online platform Roblox, our users were friends, family members, and about 100 tech enthusiasts we’d recruited via Google ads. We offered one experience. “Peak times’’ meant maybe 30 or 40 people playing at once. Erik and I were the moderators, keeping our community safe and civil.

A version of this article appeared in the March–April 2022 issue of Harvard Business Review.