Rotating API keys are good practice, but it causes issues in production. You have to reset your key in the dashboard, and then deal with downtime as you get your new API key gets deployed.
Google fixes this by keeping your old API key active for 24 hours, so you have time to get your new API key deployed.
Once you regenerate your key, Google shows you both your new key and your old one. At any time, if things go badly, you can revert back to the old key. If you don't, your old API key will expire after a day.
They also do a great job of showing dates, so it's easy to figure out exactly when your API key was generated and what's going on. No surprises from Google!