Question 1

What is a feature flag?

Accepted Answer

A mechanism that lets teams turn a feature on or off for specific users without deploying new code, effectively wrapping a feature in a remotely controllable switch.

Question 2

What is another name for a feature flag?

Accepted Answer

A feature toggle. The two terms are used interchangeably.

Question 3

What is the main benefit of feature flags?

Accepted Answer

They decouple deploying code from releasing features, giving teams precise control over rollouts and the ability to turn features on or off instantly.

Question 4

How does a feature flag work?

Accepted Answer

It is a conditional in the code that checks the flag's externally controlled state and shows or hides the feature accordingly, so the same deployed code can behave differently for different users.

Question 5

What are the main types of feature flags?

Accepted Answer

Release flags, experiment flags, operational flags, and permission flags, split between short-lived flags to remove and long-lived flags that are permanent.

Question 6

What is a kill switch?

Accepted Answer

A feature flag kept ready to instantly disable a feature that starts causing problems in production, without needing an emergency deployment.

Question 7

What is flag debt?

Accepted Answer

The accumulation of old, unused feature flags that were never removed, which makes the codebase harder to understand, test, and maintain.

Question 8

How do feature flags relate to A/B testing?

Accepted Answer

Flags are a natural mechanism for A/B tests, since they can show different versions of a feature to different randomly assigned user groups.

Question 9

What is the most important feature flag best practice?

Accepted Answer

Removing short-lived flags promptly once they have done their job, since leftover flags are the primary source of feature flag problems.

Question 10

Do feature flags add complexity?

Accepted Answer

Yes. Every active flag adds a conditional path and possible states to the code, so flags must be managed carefully to keep the system testable.

What Is a Feature Flag?

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