Feature Flags Module - Overview

Lightweight, in-process feature toggles with optional user/group targeting and percentage rollouts. All evaluation runs inside your app - no remote calls. Supports local config, JSON files, environment variables (Node.js), and Azure App Configuration (.NET only).

Packages

• .NET: PrimusSaaS.FeatureFlags (current: 2.0.0)
• Node.js: @primus-saas/feature-flags (current: 1.0.0)

Publish Status

PrimusSaaS.FeatureFlags is not yet on public NuGet. Use your internal feed or local build.

Key Capabilities

• Boolean feature toggles with global on/off
• Percentage-based rollouts (sticky by user ID)
• User and group targeting allow lists
• Time-based activation (start/end times)
• Multiple providers with local, JSON, and env support (Azure App Configuration on .NET)
• Real-time refresh with caching

Example API

GET /api/dashboard
Headers: Authorization: Bearer <JWT>
Response 200:

{
  "dashboard": "new",
  "flags": {
    "NewDashboard": true,
    "BetaFeature": false
  }
}

Quick Install

# .NET
dotnet add package PrimusSaaS.FeatureFlags

# Node.js
npm install @primus-saas/feature-flags

.NET Example

using PrimusSaaS.FeatureFlags;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddPrimusFeatureFlags(opts =>
    builder.Configuration.GetSection("PrimusFeatureFlags").Bind(opts));

var app = builder.Build();
app.MapControllers();
app.Run();

appsettings.json:

{
  "PrimusFeatureFlags": {
    "Flags": {
      "NewDashboard": { "Enabled": true, "RolloutPercentage": 50 },
      "BetaFeature": { "Enabled": true, "EnabledForUsers": ["user-123"] }
    }
  }
}

Node.js Example

import { FeatureFlagService } from '@primus-saas/feature-flags';

const featureFlags = new FeatureFlagService({
  flags: {
    newDashboard: {
      enabled: true,
      description: 'Enable the new dashboard UI',
    },
    betaFeature: {
      enabled: false,
      rolloutPercentage: 25,
      enabledForGroups: ['beta-testers'],
    },
  },
});

if (featureFlags.isEnabled('newDashboard')) {
  console.log('New dashboard is enabled!');
}

Controller Example

public class DashboardController : ControllerBase
{
    private readonly IFeatureFlagService _flags;
    public DashboardController(IFeatureFlagService flags) => _flags = flags;

    [HttpGet]
    public IActionResult Get()
    {
        var enabled = _flags.IsEnabled("NewDashboard");
        return Ok(new { dashboard = enabled ? "new" : "legacy" });
    }
}

Rollout

Use percentage rollouts to gradually enable a feature while keeping evaluations sticky per user.

{
  "PrimusFeatureFlags": {
    "Flags": {
      "NewDashboard": { "Enabled": true, "RolloutPercentage": 25 }
    }
  }
}

User Targeting

Target specific users or groups with allow lists.

{
  "PrimusFeatureFlags": {
    "Flags": {
      "BetaFeature": {
        "Enabled": true,
        "EnabledForUsers": ["user-123"],
        "EnabledForGroups": ["beta-testers"]
      }
    }
  }
}

Providers

.NET Providers

Provider	Configuration
InMemory (default)	Flags from appsettings.json
JsonFile	Provider: "JsonFile", JsonFilePath: "flags.json"
Azure App Configuration	Provider: "AzureAppConfiguration"

Node.js Providers

Provider	Configuration
memory (default)	Flags from constructor config
json	provider: "json", jsonFilePath: "./flags.json"
env	provider: "env", envPrefix: "FEATURE_"

See Also

• Feature Flags Quick Start
• Feature Flags Advanced
• Identity Validator (user context for targeting)