A Simple Analogy

Feature flags are like circuit breakers for features. You can flip switches on/off without changing code, test with real users gradually, and rollback instantly if problems occur.

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What Are Feature Flags?

Feature flags are toggles that enable/disable features without code changes. Azure App Configuration manages them centrally for all environments.

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Why Use Feature Flags?

• Gradual rollout: Enable for 10% users, then 50%, then 100%
• A/B testing: Compare old vs. new features
• Quick rollback: Disable broken feature instantly
• No redeployment: Change behavior without deployment
• Experimentation: Test with real users safely

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.NET Implementation

var builder = WebApplication.CreateBuilder(args);

// Load from App Configuration
builder.Configuration.AddAzureAppConfiguration(options =>
{
    options.Connect(builder.Configuration["AppConfig:ConnectionString"])
        .ConfigureFeatureManagement();
});

builder.Services.AddFeatureManagement();

var app = builder.Build();

[ApiController]
[Route("api/[controller]")]
public class OrdersController : ControllerBase
{
    private readonly IFeatureManager _featureManager;
    
    [HttpPost]
    public async Task<IActionResult> CreateOrder(CreateOrderDto dto)
    {
        // Use new checkout if enabled
        if (await _featureManager.IsEnabledAsync("NewCheckout"))
        {
            return await _orderService.CreateOrderAsync(dto);
        }
        
        return await _orderService.CreateOrderLegacyAsync(dto);
    }
}

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Practical Example

public class FeatureService
{
    private readonly IFeatureManager _featureManager;
    
    public async Task<OrderResponse> ProcessOrderAsync(Order order)
    {
        // Feature: Enhanced payment validation
        if (await _featureManager.IsEnabledAsync("EnhancedPaymentValidation"))
        {
            await ValidatePaymentAsync(order);
        }
        
        // Feature: Loyalty rewards
        if (await _featureManager.IsEnabledAsync("LoyaltyRewards"))
        {
            await ApplyLoyaltyPointsAsync(order.UserId, order.Total);
        }
        
        return new OrderResponse { Status = "Processed" };
    }
}

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Targeting Specific Users

// Target 50% of users
var targetingContext = new TargetingContext
{
    UserId = userId,
    Groups = new List<string> { "beta-testers" }
};

if (await _featureManager.IsEnabledAsync("NewDashboard", targetingContext))
{
    // Show new dashboard
}

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Best Practices

1. Plan rollout: 10% → 25% → 50% → 100%
2. Monitor metrics: Track feature performance
3. Clean up flags: Remove old/unused flags
4. Document flags: Explain purpose and status
5. Set expiration: Remove flags after period

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Related Concepts

• Canary deployments
• Blue-green deployments
• A/B testing frameworks
• Feature flag management tools (LaunchDarkly)

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Summary

Azure App Configuration feature flags enable safe feature deployment without code changes. Use gradual rollout to test with real users and rollback instantly if needed.