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Long-Lived Feature Flags

Long-lived flags are permanent flags that remain in your application indefinitely. They're used for ongoing feature management and operational control.

Common Use Cases​

1. Kill Switches​

Kill switches are emergency controls that let you disable features or entire system components:

  • Disable problematic features quickly
  • Manage system load during incidents
  • Control access during maintenance
  • Implement graceful degradation

For example:

if (flagsmith.hasFeature("maintenance_mode")) {
    showMaintenancePage();
} else {
    showNormalContent();
}

2. Feature Management​

Use flags with segments to control feature access:

  • Toggle features by subscription tier
  • Enable features for specific user groups
  • Control feature access by region/locale
  • Manage feature availability by app version

Example with segments:

// User with enterprise_plan trait will see the feature
if (flagsmith.hasFeature("advanced_analytics")) {
    showEnterpriseFeatures();
}

3. Configuration Management​

Use flag values to manage configuration:

  • API endpoint URLs
  • System limits and thresholds
  • Feature configuration parameters
  • Regional settings

Implementation Best Practices​

1. Naming and Organization​

Use clear, permanent-focused names:

feature_enterprise_analytics
kill_switch_api_v2
config_rate_limit

Use tags for organization:

  • kill-switch
  • config
  • permanent

2. Documentation​

Document thoroughly:

  • Purpose and use cases
  • Impact when disabled
  • Related segments/configurations
  • Owner and responsible team

3. Protection Mechanisms​

Prevent accidental changes:

4. Monitoring​

Keep track of usage and impact:

  • Monitor through Flag Analytics
  • Set up alerts for critical flag changes
  • Track dependencies in your system
  • Regular audits of flag states

Maintenance Guidelines​

  1. Regular Review

    • Validate flag configuration monthly
    • Update documentation as needed
    • Review segment rules and conditions
    • Check for obsolete configurations

  2. Testing

    • Regular testing of kill switches
    • Validate segment rules
    • Test default states
    • Verify degradation paths

  3. Change Management

    • Use Change Requests for updates
    • Schedule changes during low-impact windows
    • Coordinate changes across teams
    • Document all modifications

  4. Cleanup

    • Archive truly obsolete flags
    • Consolidate similar flags
    • Remove unused segments
    • Update documentation

Tools and Features​

Flagsmith provides several tools for managing long-lived flags:

  1. Protection

    • Protected tags
    • Change Requests
    • Flag Owners
    • Environment-specific settings

  2. Monitoring

    • Flag Analytics
    • Change history
    • Audit logs
    • Usage tracking

  3. Management

    • Scheduled changes
    • Segment controls
    • Environment overrides
    • API access