Feature Flag Service

Overview

This project is a Feature Flag Service built as part of an OJT project.

A Feature Flag system allows developers to enable or disable features dynamically without redeploying the application. This helps teams release features safely, perform experiments, and quickly disable problematic functionality.

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Problem Statement

Modern applications frequently release new features. Deploying code every time a feature needs to be enabled or disabled increases risk and downtime.

A Feature Flag Engine solves this problem by allowing features to be controlled dynamically based on rules such as:

• User targeting
• Country targeting
• App version targeting
• Percentage rollout
• Environment control (dev / staging / production)

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Tech Stack

Backend

• Go (Golang)
• Gin Web Framework
• PostgreSQL
• pgx PostgreSQL Driver

Tools

• Git & GitHub
• Postman / Thunder Client
• Docker (planned)
• React Admin Dashboard (planned)

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System Architecture

Client Application
        │
        ▼
   REST API (Gin)
        │
        ▼
  Business Logic Layer
        │
        ▼
 Repository Layer
        │
        ▼
   PostgreSQL Database

The backend follows a layered architecture:

Handlers → Services → Repository → Database

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Project Structure

feature-flag/
│
├── backend
│
│   ├── cmd
│   │   └── main.go
│
│   ├── config
│   │   └── db.go
│
│   ├── models
│   │   └── feature_flag.go
│
│   ├── handlers
│   │   └── flag_handler.go
│
│   ├── services
│   │   └── flag_service.go
│
│   ├── repository
│   │   └── flag_repository.go
│
│   └── router
│       └── router.go

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Database Schema

Table: feature_flags

Column	Type	Description
id	SERIAL	Primary key
name	VARCHAR	Feature flag name
enabled	BOOLEAN	Global flag state
environment	VARCHAR	dev / staging / prod
rollout_percentage	INT	Percentage rollout
rules	JSONB	Targeting rules
kill_switch	BOOLEAN	Emergency disable
created_at	TIMESTAMP	Creation time

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API Endpoints

Health Check

GET /health

Response

{
  "message": "Feature Flag Service is running"
}

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Create Feature Flag

POST /flags

Example Request

{
  "name": "new_ui",
  "enabled": true,
  "environment": "production",
  "rollout_percentage": 50,
  "rules": "{}",
  "kill_switch": false
}

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Get All Feature Flags

GET /flags

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Running the Project

Clone Repository

git clone https://github.com/YOUR_USERNAME/feature-flag-service.git

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Navigate to Backend

cd backend

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Install Dependencies

go mod tidy

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Run the Server

go run cmd/main.go

Server runs on:

http://localhost:8081

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Testing APIs

You can test APIs using:

• Postman
• Thunder Client
• cURL

Example

GET http://localhost:8081/flags

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Current Progress

Completed

• Backend project setup
• Gin server setup
• PostgreSQL database integration
• Feature flags table
• Create feature flag API
• Get feature flags API

Upcoming Features

• Get feature flag by ID
• Update feature flags
• Delete flags
• Rule evaluation engine
• Percentage rollout logic
• React Admin Dashboard
• Docker deployment
• Cloud deployment

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Author

Kumar Aditya
OJT Project – Feature Flag Service