A/B Testing
Marketing Incrementality 101
How do advertisers uncover the true business impact of their spend?
Learn more
What is feature flag-driven development?
Learn about feature flag-driven development, its benefits, implementation, and best practices. See how Eppo simplifies feature management for data-driven releases.
Using feature flags is pretty much the standard when rolling out new features. That’s why choosing a development strategy that revolves around this technique is a great way of making sure feature releases have the result you’re expecting.
We’re talking about feature flag-driven development.
In this primer, we’ll discuss why feature flag-driven development is such a great strategy and how it can have a real impact both on your user’s customer experience and your revenue numbers.
We’ll go over:
- A clear-cut definition of feature flag-driven development
- It's core components and how they work
- Key benefits of using feature flag-driven development
- A quick guide showing you how to implement this development technique
- Some best practices to keep in mind during implementation
- Common pitfalls and how to avoid them
Let’s begin with a quick definition.
What is feature flag-driven development?
Feature flag-driven development is a software development technique where new features are wrapped in conditional code blocks called feature flags. These flags act like switches, allowing developers to turn features on or off without needing to redeploy the entire application.
This approach gives teams immense control over how and when features are released. They can roll out features gradually to subsets of users, minimizing risk and gathering real-world feedback before a full launch.
For example, a new recommendation engine could be enabled for a small percentage of users to gauge its effectiveness before making it available to everyone.
Additionally, feature flags allow for real-time adjustments. Developers can quickly disable features if issues arise or tailor the user experience based on specific criteria. Imagine having the ability to instantly activate a promotional banner for a special sale, but only for users in a specific region. Feature flags make this kind of dynamic control possible.
What are the core elements of feature flag-driven development?
To fully grasp how feature flag-driven development works, let's dive into the three key building blocks:
1. Feature flags
At their most basic level, feature flags are simple "true" or "false" (boolean) toggles built into your code. They work like this:
- Flag is off: The new feature is hidden from your users, even if the code for it is already included in your application.
- Flag is on: The new feature is activated, and users can interact with it.
This simple concept gives you the power to decide when and how features become visible.
2. Flag management systems
While you could technically manage feature flags with basic code, dedicated flag management systems make the process much more powerful. These platforms offer:
- Dashboards: A centralized hub to create, organize, and track all your feature flags.
- Targeting: Tools to define precise rules about who sees which features (think user location, subscription level, device type, etc.).
- Monitoring: To track metrics and insights and measure the impact of your features when they're active.
3. Deployment pipeline integration
Results start to become more evident when feature flags are woven into your continuous integration and continuous deployment (CI/CD) processes. Here's how it works:
- Continuous integration (CI): Every time you push code changes, your automated testing happens as usual, even if some features are behind inactive flags. This lets you catch issues early.
- Continuous deployment (CD): You can safely push these updates to production at any time because the new, flag-wrapped bits of code won't affect users yet.
- Controlled release: When you're ready to expose a new feature, you turn its flag on (often through the management system dashboard) — no code redeployment needed.
Why use feature flag-driven development?
Feature flags transform the way software is built and released. Here are some of the most significant advantages:
1. Incremental rollouts
Instead of releasing a whole new feature to everyone at once, flags let you roll it out gradually. Start with a small percentage of users, monitor how things go, and collect feedback. If everything looks good, slowly expand the rollout. This approach helps you:
- Find issues early: Problems that slip through testing are less likely to cause widespread disruption if you're rolling out to a small group first.
- Measure real-world impact: See how the new feature actually affects user behavior and key metrics.
2. Risk mitigation
We all know the fear of a big release going bad. Feature flags can act as emergency "off" switches. Did you discover a critical bug in your fancy new feature? Disable its flag instantly, and the problem goes away for your users. No frantic code rollback, no all-hands-on-deck panic.
This means you can:
- Release code more confidently: Deploy code updates even when features aren't 100% complete yet, knowing you have a way to hide them if needed.
- Respond quickly to issues: Minimize downtime and negative user experiences by disabling a problematic feature in seconds.
3. A/B testing
Apart from letting you turn features on and off, having a feature flag-driven development strategy makes it easy to try different variations through A/B testing. This means that with a feature flag system, you can:
- Test with real users: See how different segments respond to variations of your feature in a live setting.
- Compare results: Track metrics to determine which version performs best according to your goals.
- Iterate and improve: Use these insights to further refine your feature for the best possible outcome.
How to implement feature flag-driven development
The shift to feature flag-driven development requires some adjustments to your process, a little planning, and the right tools. Let's break down the key steps required to successfully integrate this methodology into your workflow.
1. Setting up feature flags
Getting started with feature flags involves some key choices and integrating them directly into your codebase. Here's how to approach this:
- Choosing a system: Feature flag management systems give you a centralized dashboard for creating, organizing, and tracking your flags.
Explore open-source tools or consider platforms like Eppo for features like targeting, experimentation, and in-depth analysis.
- Wrapping your features: Within your code, the mechanism for using flags usually involves simple if-else logic. You'll check the flag's status (from your management system) and execute different code paths depending on whether it's on or off.
- Starting simple: Begin with a few non-critical flags to get hands-on experience and ensure your chosen system works smoothly within your workflow.
2. Integrating with CI/CD pipelines
Feature flags become truly powerful when they're baked into your continuous integration and continuous development processes. Consider these factors:
- Automate flag creation: Ideally, your CI/CD pipeline should automatically create new feature flags when new development branches are opened, or features are marked as ready for testing.
- Deployment strategies: You'll need to decide if feature flags should stay in your code even after a feature is public. Some teams have policies to auto-remove flags after a certain timeframe to avoid technical debt.
- Establish review processes: Regular flag audits are crucial. When a feature is permanently released, its flag should be retired. This keeps your codebase clean and your management system organized.
3. Managing feature flag lifecycles
Treating feature flags with care throughout their entire lifecycle prevents headaches and maximizes their benefits. Here's what to keep in mind:
- Document everything: Thorough documentation explaining each flag's purpose, who created it, and its intended usage is essential, especially for onboarding new team members.
- Plan for flag retirement: Have a predefined plan for how long flags should remain active after a feature is fully released or if the project is abandoned. Regular cleanups prevent a buildup of unnecessary flags.
What are some best practices for feature flag-driven development?
1. Have clear naming conventions
Choosing clear and descriptive names for your flags is more important than it might seem initially. A good naming system makes it a breeze to understand what each flag controls, its current status, and even who created it. Consider a structure like this:
- Feature name: A short description of the feature (e.g., "new_search")
- Status: Is it active, in testing, or retired? (e.g., "testing")
- Optional: Date or relevant version number
Example: new_search_testing_20240509
This kind of structure makes managing a large number of flags much simpler.
2. Monitor the metrics to measure impact
Feature flags aren't just about release control — they also help you understand how your changes really affect users. Make sure you have monitoring in place to track key metrics when a flag is active. Here's what to watch for:
- Performance: Monitor for any performance regressions that might negatively impact user experience. If the feature introduces unexpected load or slows down other parts of the application, you might need to optimize the code or consider a staged rollout to a smaller user base.
- User behavior: Do users engage with the feature as expected? Are there any changes to main conversion goals? Track how users interact with the new functionality.
Are they clicking buttons, exploring different options, or completing desired actions? This will tell you if the feature resonates with your target audience and achieves its intended purpose.
- A/B test results: If you're running variations of a feature (different designs, functionalities, etc.), track which one performs best according to your chosen goals. Feature flags allow you to test A/B variations with specific user segments.
By monitoring metrics like conversion rates, completion times, or user satisfaction scores, you can identify the variation that delivers the best results for your target audience.
3. Keep stakeholders in the loop
Feature flags touch many aspects of the development and release process. Smooth communication is crucial to prevent surprises and misunderstandings. Make sure the following people are kept informed:
- Developers: The team needs to know what flags exist, what they control, and how to work with them.
- Product managers: They'll be planning rollouts and making release decisions based on flag status and the data they generate.
- Marketing/sales: These teams may be planning campaigns or announcements tied to new feature releases. Keeping them aware of timelines helps everyone stay in sync.
Common mistakes during feature flag-driven development
1. Technical debt due to outdated flags
It's easy to get excited about using feature flags to control releases. However, just like any code, feature flags can become a problem if not managed carefully. Leaving outdated flags in your codebase long after a feature is public is a recipe for technical debt.
This extra layer of conditional logic makes your codebase harder to understand and maintain over time. Additionally, old flags might unexpectedly interact with new code, leading to bugs that are difficult to track down.
To prevent this, make regular audits of your flags a part of your process. Remove flags for fully released features and set policies on how long a flag should remain active even after the feature is no longer under development.
2. Getting tangled up in the complexity of feature flag management
Feature flags introduce a new layer of complexity into your system. As their use grows, testing becomes more involved, since you need to test various combinations of flags being active and inactive to ensure everything works as intended.
Additionally, keeping track of what each flag does, who owns it, and its intended lifespan can be tricky, especially in larger teams.
To manage this complexity, thorough documentation of each flag's purpose is crucial. Using a centralized feature flag management system can help visualize and organize all your flags.
Lastly, consider implementing a global "kill switch" as a safety net. This would allow you to instantly disable all feature flags if a major issue arises, minimizing potential damage and giving your team time to troubleshoot effectively.
Next steps
You should now understand how feature flags give you control over releases, enable experimentation, and let you tailor user experiences.
Eppo is a powerful experimentation and feature management platform that takes feature flagging to the next level, empowering you to unlock the full potential of feature flag-driven development.
Other feature flagging tools can leave room for uncertainty when it comes to A/B testing and analyzing results. Eppo prioritizes statistical rigor, delivering clarity and transparency throughout the entire process.
What’s more, Eppo integrates effortlessly with your existing data warehouses (Databrick, Redshift, BigQuery, Snowflake, and more).
This means data is being pulled from your internal source of truth. This minimizes setup time, letting you start experimenting immediately and seeing results sooner.
Here’s how Eppo aids you in your feature flag-driven development strategy:
- Strategic rollout capabilities: Leverage Eppo's feature flagging to carry out targeted feature releases, from gradual rollouts to canary launches. Collect usage data and refine your features based on real user feedback.
- Sophisticated experimentation: Use Eppo’s flag management to design robust experiments. Easily set up A/B or multivariate tests, targeting user segments based on attributes, behaviors, and more.
- Rigorous analysis for informed decisions: Eppo's statistical engine analyzes your results in the context of your warehouse data, revealing clear performance differences between your feature variations.
Learn about feature flag-driven development, its benefits, implementation, and best practices. See how Eppo simplifies feature management for data-driven releases.
Table of contents
Ready to go from knowledge to action?
Talk to our team of experts and see why companies like Twitch, DraftKings, and Perplexity use Eppo to power experimentation for every team.
Get a demo
.webp)
