Checkgate is a blazing-fast, open-source feature flag engine designed for teams who refuse to compromise on performance or privacy. By evaluating feature toggles locally in sub-microseconds, Checkgate completely eliminates network latency, expensive API round-trips, and SaaS vendor lock-in.
It is proudly built in Rust and ships with native SDKs for Node.js (NAPI), browsers (WebAssembly), React Native (JSI), and Flutter (FFI). A persistent SSE stream propagates flag changes to every connected SDK instance in under 50 ms.
- Sub-microsecond evaluation — flags are evaluated entirely in local memory
- Real-time updates — SSE push, not polling; changes land in < 50 ms
- Targeting rules — match by any user attribute (
email,plan,region, …) - Percentage rollouts — deterministic MurmurHash3 bucketing; sticky and independent per flag
- Rust evaluation core — compiled to NAPI, WASM, JSI, or FFI depending on platform
- Self-hosted — single binary + PostgreSQL + Redis; your data never leaves your infra
| Topic | Link |
|---|---|
| Why Checkgate / comparisons | What is Checkgate? |
| System architecture | Architecture |
| Flags, rules, rollout concepts | Core Concepts |
| Step-by-step setup | Getting Started |
| REST API + SSE stream reference | API Reference |
| Node.js SDK | SDK: Node.js |
| Web (WASM) SDK | SDK: Web |
| React Native (JSI) SDK | SDK: React Native |
| Flutter (FFI) SDK | SDK: Flutter |
| Docker, AWS, env vars | Self-Hosting |
| Enterprise Setup & Migration | Enterprise Setup & Migration |
See CONTRIBUTING.md.
MIT — see LICENSE.