What do you use to manage features and limits in your SaaS app?

Do you use an experimentation tool like LaunchDarkly and Optimizely to set up feature flags? Arguably, these are unsuitable for tracking limits. Sure, you could do a hack and slap on additional metadata onto the events. But you would still need to follow up with: tying your features and limits to your plans somewhere, periodically extracting the experiment data, aggregating the counts by user and writing custom code to gate your users. Or do you roll your own custom usage tracking and feature gating logic in your code? How do you keep things clean when you have a super complex pricing matrix? Or consistent across multiple projects / codebases? Disclaimer: I built Limiter, an open source platform for applying feature limits to your SaaS business. I'm mostly seeking feedback, low-key wishing for users.