HKSM
Feature Toggle
A method to switch features on or off in the live environment through configuration or flags, avoiding a new deployment.
Key Points
- Controlled by runtime flags or configuration, not by code changes.
- Decouples deployment from release, enabling gradual rollouts and experiments.
- Acts as a fast rollback or kill switch for risky functionality.
- Requires governance: clear naming, safe defaults, monitoring, and timely cleanup to limit technical debt.
Example
A Scrum team ships a new payment option with the feature turned off by default. After verifying production health, the product owner enables it for 5% of users. Metrics look good, so they ramp up to 50%. A spike in errors appears, so the team disables the toggle immediately, restoring stability without redeploying code.
PMP Example Question
A team wants to release a new search algorithm to 10% of users, watch KPIs, and turn it off instantly if issues occur, all without another deployment. What practice should the project manager recommend?
- Use feature toggles managed by configuration.
- Perform a blue-green deployment with DNS cutover.
- Defer the feature to the next sprint and freeze scope.
- Hard-code the new algorithm as the default and update acceptance criteria.
Correct Answer: A — Feature toggle
Explanation: Feature toggles allow enabling or disabling functionality at runtime without redeploying. Blue-green swaps environments, not individual features; the other options do not address controlled, rapid rollback.
