Feature Flags:
The Definitive Guide

Feature flags have become a staple for software development teams to release features quickly and safely. Feature flags can be used for a wide range of purposes and are referred to in a number of ways from feature toggles to feature flippers but the core concept remains the same.

This guide will take you through the concept of feature flags, why and how they are used by teams today, their implementation and some of their pros and cons.

What are feature flags?

Feature flags are a software development tool whose purpose is to turn functionalities on or off in order to safely test in production by separating code deployment from feature release.

Thus, a feature flag ranges from a simple IF statement to more complex decision trees, which act upon different variables.

There are many types of feature flags, categorized based on their dynamism and longevity that serve different purposes. 

Short vs long-lived feature flags

When we talk about longevity, we are referring to feature flags that are either meant to stay in your system for a short period of time while other flags could stay for years. 

For example, feature flags may be short-lived to temporarily deploy new changes and test in production while other long-term flags, such as kill switches, remain in your system longer. Therefore, you will need to manage different feature toggles or flags depending on how they’re deployed.

Keep reading: Short vs Long-lived Feature Flags

Dynamic vs static feature flags

In terms of dynamism, which is how often you need to modify a flag in its lifetime, there are two categories of flags:

• Dynamic- allow their value to be changed at runtime.
• Static- only change through actual code changes or configuration file changes.

To learn more about the differences between static and dynamic flags and where to store them depending on which category they fall under, read our best practices article on where to store feature flags.

We can further break down feature flags into various categories of toggles, which should be managed differently. In other words, you will need to manage different feature toggles or flags depending on how they’re deployed. The main categories are: 

• Release toggles
• Experimental toggles
• Operational toggles
• Permission toggles

For more details on these different categories of feature toggles, refer to this article.

Why use feature flags?

Feature flags can be employed across a wide range of use-cases, from the most simple to more advanced uses as various teams such as engineering and production teams across organizations have begun to recognize their benefits in their software release strategy.

Benefits of feature flags

There is no denying that feature flags have become a necessity when releasing new features rapidly and safely. Having an efficient feature management system can help streamline release processes.

The following is just some of the ways that they can bring value to your software development and release processes.

Challenges of feature flags

You can never have too much of a good thing and yet nothing is perfect. There are times when you may run into some pitfalls while using feature flags so while their use is encouraged and brings great benefit to your team’s workflow, proceed with caution, especially if you’re relying on an in-house feature flagging platform.

Integrate feature flags in software development

Software usually goes through a series of stages or phases to produce high quality software through the software development life cycle (SDLC).

The phases incorporated depend on the methodology used but the basic principles of SDLC are more or less the same.

For more information about the software life cycle, you can read more in our article about the different stages of the SDLC in conventional and Agile methodologies.

Based on the above, at the beginning of any software development process, teams and organizations must decide what methodology they will adopt to ensure high quality products. Waterfall and Agile are two of the most popular methods though Agile is rapidly gaining traction over Waterfall.

Feature Flag best practices

There are many practices that need to be applied when working with feature flags. The following are some best practices that you will need to consider and implement to make your feature flag journey as smooth as possible: