Roblox RBLX had an amazing second quarter, with impressive growth in users and paying users. However, the strength was driven by so-called viral hits, which could lead to unevenness in future growth.

(Bloomberg/Cecilia D’Anastasio) — Roblox Corp., the popular video-game platform, reported a larger-than-expected jump in active users for the first quarter, benefiting from efforts to attract new ...