Flag Dependencies

Flag dependencies define relationships between flags to ensure evaluation order. The result of each flag's evaluation is then passed to all subsequent evaluations to decide if dependent flags should evaluate based on the result of the dependency.

Flag dependencies help implement:

• Flag prerequisites
• Mutual exclusion groups
• Holdout groups

Flag prerequisites

Available for flags and experiments.

Flag prerequisites is a generic implementation of flag dependencies that lets any flags or experiments depend on any other flags or experiments. Evaluation of the prerequisites can check specific variants or target users who weren't included in the prerequisite flag or experiment.

Use flag prerequisites to:

• Actively develop large feature releases with many developers and teams.
• Build provisioning for users to primary SKUs with add-ons.
• Simplifying complex feature flag logic in code.
• Build complex hierarchies of mutually exclusive experiments which start at different times

For more information, go to Flag Prerequisites

Mutual exclusion groups

Available for experiments only.

A mutual exclusion group ensures that your users are only included in a single experiment. In Experiment, a mutual exclusion group defines multiple slots, each with a percentage of traffic allocated to that slot. The mutual exclusion group is actually just a flag with a variant for each slot. Experiments in the group add a dependency on one or more (variants) of the mutual exclusion group flag.

The variant result of a mutual exclusion group's evaluation isn't returned and isn't assigned as a user property.

For more information, go to Set up and run mutually exclusive experiments

Holdout groups

Available for experiments only.

A holdout group withholds a percentage of traffic from a group of experiments. This allows measurement of the long-term and combined impact of multiple experiments. Experiment implements a holdout group using a flag with two variants: holdout and on. The holdout percentage that's defined when the group is created is allocated to the holdout variant. Experiments in the group depend on the holdout group's variant on.

The variant result of a holdout group's evaluation isn't returned. However, it's assigned as a user property to enable holdout analysis.

For more information, go to Holdout Groups.

Local evaluation support

Flag dependencies (mutual exclusion and holdout groups) is only supported after certain versions of Amplitude SDKs.