Activation Rules

Activation rules determine who sees a feature in a given environment. Each flag has independent rules for each environment.

How Rules Work

flowchart TD
    A["Is the flag enabled?"] -->|no| X[false]
    A -->|yes| B["Context matches?<br/>(all attributes AND)"]
    B -->|yes| D["Hash of userId<br/>below rollout percentage?"]
    B -->|no| C["In any segment?<br/>(OR between segments)"]
    C -->|yes| D
    C -->|no| X
    D -->|yes| Y[true]
    D -->|no| X

1. State — if the flag is disabled, the check ends at false.
2. Context — user attributes (country=US, plan=premium). All must match — AND.
3. Segments — if context didn't match, attached segments are checked. The flag enables if the user is in any one of them — OR between segments.
4. Rollout — a deterministic hash of flagKey + userId is compared against the rollout percentage. Below → true.

Context Constraints

Constraints match attributes passed to the SDK. If context doesn't match — move on to segments.

{
  "constraints": [
    { "field": "country", "operator": "in", "values": ["US", "CA"] },
    { "field": "plan", "operator": "eq", "values": ["premium"] }
  ]
}

All rules within a group use AND logic. If an attribute is missing from the context, the rule returns false.

Segments

Reusable user groups. Attach them to activation rules by reference — no need to duplicate conditions across flags.

A flag can reference multiple segments — matching any one is enough (OR). See Segments.

Percentage Rollout

MurmurHash32 of flagKey + userId (or sessionId if userId is absent). The same user always lands in the same bucket.

Rules & Environments

Activation rules are configured independently per environment. The same flag can be enabled for everyone in Development and only for beta testers in Production.

Environment	Rules
Development	Enabled, 100% rollout — all developers see the feature
Production	Enabled, «Beta Testers» segment + 10% rollout — gradual launch

The SDK receives rules only for the environment its API key is bound to.

What's Next

• Flags — flag types and lifecycle
• Contexts — attributes and operators
• Segments — reusable groups
• Environments — isolation and limits