Feature flags are useful tools to manage rollouts, perform experimentation, and much more. There's lots of companies doing serious stuff in this space, eg LaunchDarkly, Split, Optimizely, etc; two of my previous employers rolled their own experimentation platforms with tons of staffing.

However, I needed something way simpler and ideally free. So -- why not use Google Sheets as the backend? You can control who has access to read/edit flag values, there's audit history, it's incredibly simple to use. I intend to use this in production for a while, there's almost certainly a scale at which it won't make sense, but that'll be a problem for a different time.