What You'll Learn
Master feature flags with our battle-tested framework. From basic toggles to advanced rollout strategies, here's everything you need to ship faster and safer.
Feature flags are the difference between shipping weekly and shipping daily. After implementing feature flags across 50+ production systems, we've refined a complete framework that reduces deployment risk by 80% while enabling rapid experimentation.
Why Feature Flags Matter
Teams using feature flags ship 4x more frequently with 60% fewer rollbacks. The key insight: decouple deployment from release.
The Deployment vs. Release Problem
Most teams conflate deploying code with releasing features. Feature flags let you deploy safely and release strategically.
The Feature Flag Hierarchy
Not all feature flags are created equal. We use a 4-tier system based on risk and complexity:
Tier 1: Kill Switches (Emergency)
- Purpose: Instantly disable problematic features
- Examples: Payment processing, authentication, core business logic
- Requirements: Sub-second response time, 99.99% uptime
Tier 2: Release Toggles (Deployment)
- Purpose: Control feature visibility post-deployment
- Examples: New UI components, API endpoints, integrations
- Requirements: Fast response time, reliable evaluation
Tier 3: Experiment Toggles (A/B Testing)
- Purpose: Test different feature variations
- Examples: Pricing pages, onboarding flows, recommendation algorithms
- Requirements: Consistent user experience, statistical validity
Tier 4: Permission Toggles (Access Control)
- Purpose: Control feature access by user, role, or segment
- Examples: Beta features, premium functionality, geographic restrictions
- Requirements: User context awareness, flexible targeting
Implementation Framework
1. Flag Naming Convention
Use a consistent naming pattern that scales:
{namespace}.{feature}.{environment}
Examples:
payment.stripe-integration.prod
ui.new-dashboard.beta
experiment.pricing-page-v2.staging
Choose Your Namespace
Group related flags by product area, team, or feature category. This prevents naming conflicts and improves organization.
Use Descriptive Feature Names
The feature name should clearly indicate what it controls. Avoid abbreviations or internal jargon.
Include Environment Suffix
Even if your flag service handles environments, include them in the name for clarity.
2. Flag Lifecycle Management
Every feature flag should follow a predictable lifecycle:
Flag Lifecycle Stages
- Created with default 'off' state
- Tested in staging environment
- Deployed to production (still off)
- Enabled for internal users first
- Gradually rolled out to customers
- Monitored for performance impact
- Fully enabled or rolled back
- Removed after feature is stable
3. Rollout Strategies
Gradual Rollout (Recommended for most features)
Start with internal users, then expand to customer segments:
Week 1: Internal team (5%)
Week 2: Beta customers (25%)
Week 3: All customers (100%)
Pros
- Catches issues before widespread impact
- Allows for quick rollback if needed
- Builds confidence in the feature
- Enables data collection at each stage
Cons
- Takes longer to reach full rollout
- Requires user segmentation setup
- Can create inconsistent user experiences
- Needs careful monitoring at each stage
Percentage Rollout (Good for low-risk features)
Gradually increase the percentage of users who see the feature:
Day 1: 10% of users
Day 3: 25% of users
Day 7: 50% of users
Day 14: 100% of users
Canary Rollout (Best for high-risk changes)
Target specific user segments or geographic regions first:
- Start with your most forgiving users (internal, beta, specific regions)
- Monitor key metrics closely
- Expand only if metrics remain stable
Advanced Patterns
1. Flag Dependencies
Some features depend on others. Handle this with dependency chains:
// Feature B depends on Feature A
if (isEnabled('feature-a') && isEnabled('feature-b')) {
// Show Feature B
}
Dependency Complexity
Keep dependency chains simple. More than 3 levels of dependencies become hard to reason about and debug.
2. User Segmentation
Target features based on user attributes:
const userSegments = {
beta: user.tags.includes('beta'),
premium: user.subscription === 'premium',
region: user.country === 'US',
cohort: user.signupDate > '2024-01-01'
};
if (isEnabled('new-feature', userSegments)) {
// Show feature
}
3. Gradual Feature Rollout
Implement features that can be partially enabled:
const featureConfig = getFeatureConfig('new-dashboard');
if (featureConfig.enabled) {
if (featureConfig.showSidebar) {
renderSidebar();
}
if (featureConfig.showAnalytics) {
renderAnalytics();
}
}
Monitoring & Observability
Key Metrics to Track
Flag Evaluation Rate
< 1ms
Time to evaluate feature flag
Flag Uptime
99.99%
Feature flag service availability
Rollback Time
< 30s
Time to disable problematic feature
Monitoring Dashboard
Track these metrics in real-time:
- Flag evaluation latency - Should be < 1ms
- Flag service uptime - Should be > 99.9%
- Feature adoption rate - How quickly users adopt new features
- Error rate by flag - Errors introduced by specific features
- Performance impact - Response time changes per feature
Common Pitfalls & Solutions
1. Flag Proliferation
Problem: Too many flags create complexity and confusion.
Solution: Implement a flag cleanup process:
- Review flags monthly
- Remove flags that have been stable for 30+ days
- Archive old flags instead of deleting them
- Set up alerts for flags that haven't been toggled in 90 days
2. Inconsistent User Experience
Problem: Users see different features on different pages.
Solution: Use consistent user targeting:
- Always use the same user ID for flag evaluation
- Cache flag states per user session
- Implement sticky sessions for A/B tests
3. Performance Impact
Problem: Flag evaluation slows down application response time.
Solution: Optimize flag evaluation:
- Cache flag states locally
- Use async flag evaluation where possible
- Implement circuit breakers for flag service calls
4. Testing Complexity
Problem: Feature flags make testing more complex.
Solution: Implement flag testing strategies:
- Test with flags enabled and disabled
- Use feature flag testing tools
- Implement flag-aware integration tests
Implementation Checklist
Feature Flag Setup (Week 1)
- Choose feature flag service (LaunchDarkly, Split, custom)
- Set up development and staging environments
- Implement basic flag evaluation in application
- Create flag naming convention
- Set up monitoring and alerting
First Feature Flag (Week 2)
- Identify low-risk feature for first flag
- Implement flag in code
- Test in staging environment
- Deploy to production (disabled)
- Enable for internal team
- Monitor for 24 hours
- Roll out to customers
Advanced Patterns (Week 3-4)
- Implement user segmentation
- Set up A/B testing framework
- Create flag dependency management
- Implement gradual rollout strategies
- Set up automated flag cleanup
Tools & Services
Feature Flag Services
LaunchDarkly - Full-featured with advanced targeting
- Best for: Enterprise teams with complex requirements
- Pricing: $10/user/month
- Pros: Advanced targeting, good integrations
- Cons: Can be expensive for small teams
Split.io - Developer-focused with good performance
- Best for: Performance-critical applications
- Pricing: $5/user/month
- Pros: Fast evaluation, good developer experience
- Cons: Less advanced targeting options
Custom Solution - Build your own
- Best for: Teams with specific requirements
- Pricing: Development time
- Pros: Full control, no vendor lock-in
- Cons: Maintenance overhead, feature development
Next Steps
Ready to implement feature flags? Start with our deployment readiness assessment to identify which features are good candidates for flagging. For more on reducing deployment risk, see our guide on progressive rollouts.