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Feature Flag Service

A self-hosted feature flag service built with Rust and PostgreSQL. Create flags, target specific users, run gradual rollouts, and evaluate everything from your application through a single SDK endpoint.

What it does​

  • Toggle features across projects and environments without redeploying
  • Target users by ID, email address, or email domain
  • Roll out gradually with deterministic percentage-based bucketing
  • Kill switches — disable any flag instantly, no deploy needed
  • Evaluate flags from any application with a single HTTP call

How it works​

Your application calls POST /sdk/v1/evaluate with an SDK key and a user context. The service returns every flag state for that user in one JSON response.

POST /sdk/v1/evaluate
X-SDK-Key: sdk_your_key_here

{
  "environment": "production",
  "context": { "user_id": "user_42", "user_email": "[email protected]" }
}
{
  "flags": {
    "dark_mode":       { "enabled": true,  "reason": "User in 50% rollout" },
    "new_checkout":    { "enabled": true,  "reason": "Matched email_domain rule" },
    "premium_features":{ "enabled": false, "reason": "Flag is globally disabled" }
  }
}

Where to start​

I want to…Go to
Get something working fastQuickstart
Understand the data modelConcepts
Integrate flags into my appSDK Integration
See all API endpointsAPI Reference
Deploy on my own serverSelf-Hosting