// the find
flippercloud/flipper
🐬 Beautiful, performant feature flags for Ruby.
Flipper is the de facto feature flag library for Ruby/Rails. It handles the standard targeting primitives — boolean, actor, group, percentage of actors, percentage of time — and wraps any storage backend behind a clean adapter interface. If you're running Rails and need feature flags today, this is what you reach for.
The adapter pattern is genuinely well-designed: swap Redis for Postgres for Memcached without touching application code, and you can layer adapters (memoizable on top of Redis, failsafe on top of that). The expression system adds rule-based targeting (property comparisons, time windows) without bloating the core API. The built-in Rack UI ships with the gem — no separate service to deploy. Telemetry is opt-in and the instrumentation hooks (ActiveSupport::Notifications compatible) mean you can wire it into whatever observability stack you have.
The Cloud product is the obvious upsell target and the OSS docs increasingly point you there for anything non-trivial — audit history and environment cascading aren't really possible self-hosted. The expression system is powerful but the documentation is thin; you'll be reading source to understand what's composable. The UI is Bootstrap 4 jQuery-era HTML, functional but dated, and customization requires forking the gem or monkey-patching. Multi-adapter setups (dual_write, sync, poll) work but the interaction between them under failure conditions is not well-tested in the published specs — you're on your own if your secondary falls behind.