Checkgate is an open-source feature flag engine that evaluates flags locally — no network call, no latency, no SaaS vendor. Every flag decision happens inside your process in sub-microseconds, while a persistent SSE stream keeps every SDK instance in sync within 50 ms of a change.
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.
A flag change is written once, then pushed to every connected SDK in milliseconds — after which each isEnabled() is a local, in-process lookup.
- 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
Dashboard shown with example data for a fictional company, Vantage Robotics.
Dashboard overview — flag counts, rollout status, and recent activity at a glance.
Feature flags — tags, types, rollout percentage, and one-click enable/disable per environment.
Flag editor — targeting rules, tags, ownership, and prerequisite (dependent) flags.
Change requests — require a second reviewer before a flag change takes effect in sensitive environments; self-approval is blocked.
Cross-environment diff — see what's different between environments before promoting, with a one-click sync.
Personal access tokens — scoped, revocable API credentials for CI/CD and Terraform, as an alternative to admin-equivalent SDK keys.
Environments — isolate configuration across Production, Staging, UAT, and Development, with per-environment approval gates.
Collapsible sidebar — reclaim screen space on data-dense pages; the whole dashboard is full-width by default.
| 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 |
| Type-safe codegen CLI | @checkgate/cli |
| Edge evaluation (Workers, Fly.io) | @checkgate/edge |
| SSR / bootstrap (Next.js, Remix, …) | @checkgate/ssr |
| Terraform / OpenTofu provider | terraform-provider-checkgate |
| Kubernetes operator | checkgate-operator |
| Docker, AWS, env vars | Self-Hosting |
| Enterprise Setup & Migration | Enterprise Setup & Migration |
See CONTRIBUTING.md.
Apache License 2.0 — see LICENSE and NOTICE.
Releases up to and including v0.1.21 were published under the MIT License; that
grant is irrevocable for those versions.