Flagsmith

Flagsmith is a self‑hosted, open‑source feature flagging platform that delivers fine‑grained control over feature rollout, remote configuration, and A/B testing. From a technical standpoint it exposes a RESTful API for flag evaluation, a real‑time WebSocket endpoint for live updates, and an admin dashboard built with modern web frameworks. The system is designed to run in any private cloud or on-premise environment, with Docker images and a PostgreSQL backend that can be replicated across nodes for high availability.

Architecture

The core architecture is split into two main services:

• API Service – A Django‑based Python backend that implements the flag evaluation logic, permission model, and audit trail. It uses Django REST Framework for endpoint generation and GraphQL for flexible querying.
• Frontend Dashboard – A React/Next.js single‑page application that consumes the API, renders flag trees, and provides a visual editor for segments and rollout percentages.

Both services share the same PostgreSQL database (or any supported RDBMS) and can be scaled horizontally behind a load balancer. The API is stateless, enabling container orchestration with Kubernetes or Docker‑Compose. Real‑time updates are pushed via Django Channels over Redis, ensuring clients see flag changes instantly.

Core Capabilities

• Feature Flags & Remote Config – Boolean toggles, string/JSON values, and multivariate flags with percentage rollout. Flags can be scoped to environments, users, or segments.
• Segmentation Engine – Declarative rules (user attributes, device type, geography) evaluated on the fly; supports nested segments and logical operators.
• A/B & Multivariate Testing – Built‑in experiment framework that tracks exposure and conversion metrics, exposing a simple REST endpoint for results.
• SDKs & Integrations – 15+ client libraries (TypeScript, .NET, Java, Python, Go, Ruby, etc.) plus hooks for popular frameworks (React, Next.js). Webhooks and a public API allow integration with CI/CD pipelines, analytics tools, or custom dashboards.
• Audit & Permissions – Role‑based access control (orgs, projects, users) with granular permissions for flag creation, deployment, and monitoring.

Deployment & Infrastructure

Flagsmith ships as Docker images (flagsmith/flagsmith for the API, flagsmith/frontend) and is fully compatible with Kubernetes via Helm charts. The default Docker‑Compose stack spins up PostgreSQL, Redis, and the two services in minutes. For production, you can:

• Deploy to a private cloud (e.g., AWS ECS, GKE) with an RDS/CloudSQL database.
• Use Docker‑Swarm or Compose for smaller teams.
• Scale the API horizontally; the frontend can be served by a CDN to reduce latency.

The platform is licensed under BSD‑3, giving developers full freedom to modify and redistribute the code while retaining a permissive license for commercial use.

Integration & Extensibility

Flagsmith’s API is fully RESTful and versioned, with SDKs that wrap the endpoints in idiomatic language constructs. Custom extensions can be added by creating new Django models or overriding viewsets, thanks to the open‑source codebase. Webhooks expose flag state changes to external systems (e.g., Slack, PagerDuty). The segmentation engine accepts custom predicates, allowing integration with external attribute stores or LDAP directories.

Developer Experience

The documentation is comprehensive: separate sections for API usage, SDK integration, deployment guides, and advanced configuration. A vibrant community on Discord and GitHub issues provides rapid support. The admin UI is intuitive, offering drag‑and‑drop segment creation and real‑time flag preview. Configuration is driven by environment variables, making it easy to toggle between local dev and production settings.

Use Cases

• Canary Releases – Enable a new feature for 5% of users, monitor metrics, and ramp up safely.
• Feature Rollouts by Environment – Keep a feature disabled in staging but enabled in production without code changes.
• Remote Configuration for Mobile Apps – Push UI tweaks or API endpoint URLs without redeploying the app.
• A/B Testing – Run controlled experiments on user flows and measure conversion directly within the platform.

Advantages

Flagsmith offers a high‑performance, low‑latency evaluation engine that can be run in a single container or scaled across multiple nodes. Its BSD‑3 license removes vendor lock‑in, while the rich SDK ecosystem eliminates language barriers. Compared to proprietary SaaS solutions, self‑hosting gives developers full control over data residency and compliance, making it ideal for regulated industries. The combination of a feature‑rich API, an extensible segmentation engine, and containerized deployment positions Flagsmith as the go‑to platform for developers who need reliable feature flagging without compromising on flexibility or security.