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Module 08: Feature Flags Deep Dive

← Module 07: DataDog APM | Topic Home | Next → Module 09: Progressive Delivery

Status Difficulty Time

Stub module — Content to be generated. See the topic README for the full module map.

Table of Contents

  1. Overview
  2. Prerequisites
  3. Objectives
  4. Theory
  5. Key Concepts
  6. Examples
  7. Common Pitfalls
  8. Cross-Links
  9. Summary

Overview

This module covers feature flag systems in production depth: LaunchDarkly vs PostHog vs. homegrown solutions, flag types (boolean, multivariate), targeting rules and user segmentation, percentage-based gradual rollouts with consistent hashing, kill switches, and managing technical debt from stale flags. After this module, you will be able to design a complete feature flag taxonomy for a production system.

Difficulty: Advanced  |  Estimated time: 7 hours

Prerequisites

  • Module 07: DataDog APM (all prior modules in this topic)
  • Understanding of progressive rollouts from Module 01 introduction
  • Experience with a web framework (Flask, FastAPI, or Express)

Objectives

By the end of this module, you will be able to: (to be filled in when module is expanded)

  1. Compare LaunchDarkly, PostHog, and homegrown feature flag implementations across key dimensions
  2. Design a flag taxonomy (naming conventions, ownership, lifecycle) for a production system
  3. Implement boolean and multivariate flags with user targeting rules
  4. Implement consistent hash-based percentage rollouts that provide stable user assignment
  5. Design and execute a kill switch procedure for a production incident
  6. Identify and remove stale flags, reducing flag technical debt

Theory

[!NOTE] This module is a stub. Full theory content will be generated when this module is expanded.

Planned content: LaunchDarkly vs PostHog vs. homegrown solutions, flag types (boolean/multivariate), targeting rules, gradual rollouts, kill switches, technical debt from stale flags.

Planned Sections

  1. Flag System Architecture — evaluation models (server-side vs. client-side), SDK patterns, consistency guarantees
  2. Flag Types — boolean, string, number, JSON multivariate; when to use each
  3. Targeting Rules — user attributes, group membership, percentage-based, combined rules
  4. Consistent Hashing for Rollouts — why naive random assignment fails; how to ensure stable user experience
  5. Kill Switches — design patterns for instant feature disablement; alerting integration
  6. Flag Lifecycle and Technical Debt — creation, rollout, cleanup; flag debt metrics

Key Concepts

To be filled in when module is fully generated.

Examples

To be filled in when module is fully generated.

Common Pitfalls

To be filled in when module is fully generated.

  • [[feature-flags-monitoring/modules/07_datadog-apm]] — Previous module; DataDog monitoring integrates with flag change detection
  • [[feature-flags-monitoring/modules/09_progressive-delivery]] — Next module; progressive delivery builds on the flag patterns in this module
  • [[feature-flags-monitoring/modules/01_introduction]] — Introduction to feature flag concepts that this module expands on

Summary

To be filled in when module is fully generated.