Thousands of WhatsApp users opened the app this week and found themselves locked out completely, with a message saying their account was “under review.” Meta has since restored access, but the scare is a good reminder of what happens when the one app you rely on for everything suddenly stops working. If you’re like most WhatsApp users, it’s not just a chat app. When an app that central goes down, even for a few hours, there’s often no backup plan. WhatsApp is working again, but nothing says it will be the last time an app this big trips over itself.