What This Stack Does
Feature flags have evolved from simple on/off toggles to sophisticated experimentation platforms that drive product decisions. This stack provides a complete solution using open-source tools that can be self-hosted, giving teams full control over their feature management and experimentation data without vendor lock-in or per-seat pricing.
Experimentation and Lightweight Toggles
GrowthBook serves as the experimentation engine, connecting directly to your data warehouse to compute A/B test results with proper statistical rigor. For teams that need rigorous experimentation with Bayesian or frequentist analysis, GrowthBook provides the analytical capabilities that distinguish data-driven product development from guesswork.
Flagsmith complements GrowthBook as a lightweight feature flag platform for teams or services that need simple toggles without the experimentation overhead. Its BSD-3-Clause license and Docker Compose deployment make it the fastest path to production feature flags. Use Flagsmith for operational flags and GrowthBook for experimental flags.
Caching and Observability Integration
Valkey provides the caching layer that ensures feature flag evaluations add zero latency to your application. Both GrowthBook and Flagsmith SDKs can cache feature definitions locally, but for server-side evaluations and shared state, a fast key-value store keeps flag checks under a millisecond.
Highlight.io or SigNoz adds observability to understand how feature flag changes impact application performance and user experience. Session replay from Highlight.io shows exactly what users experience during experiments, while SigNoz provides backend performance monitoring to ensure flag-gated features do not introduce regressions.
The Bottom Line
This stack replaces LaunchDarkly ($800+/mo for teams), Statsig, and Split.io with zero software licensing costs. The trade-off is operational responsibility for self-hosting, but Docker Compose deployments make this manageable for most engineering teams. The total cost is limited to compute infrastructure for hosting the services.