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Documentation Index

Fetch the complete documentation index at: https://docs.nexus.westyx.cloud/llms.txt

Use this file to discover all available pages before exploring further.

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What are feature flags?

Feature flags let you toggle behaviour in your application without a deployment. Nexus flags support:
  • Boolean on/off - the simplest use case
  • Scheduling - automatically enable or disable at a specified time (starts_at / ends_at)
  • A/B rollout - enable for a percentage of users with optional targeting rules
  • Live push - changes propagate to connected SDK instances within milliseconds

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Reading flags

All SDKs expose a GetFlag / getFlag / get_flag method that returns a boolean with a default fallback if the flag is not found. 
enabled := client.GetFlag("new.checkout", false)

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A/B rollout

The AB Testing add-on (available on s tier and above) enables percentage-based rollout with optional targeting rules. Use evaluateAB to evaluate multiple flags at once for a specific user: 
results, err := client.EvaluateAB(ctx, []string{"checkout-v2", "new-sidebar"}, userID, map[string]string{
    "plan": "pro",
    "country": "HU",
})
evaluateAB returns { "checkout-v2": true, "new-sidebar": false } - stable for the same userID across calls (FNV-64 bucket).
A/B Testing requires the AB Testing add-on to be active on the project. A 403 response with ab_addon_not_active indicates the add-on is not enabled.

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Scheduling

Flags can be scheduled to turn on or off automatically:
  • starts_at - enable the flag at this UTC timestamp
  • ends_at - disable the flag at this UTC timestamp
The schedule is enforced server-side; the SDK always returns the current state.

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Key names

Flag keys follow the same pattern as secrets and configs: ^[a-zA-Z]([a-zA-Z0-9_.:-]*[a-zA-Z0-9])?$

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Targeting rules

When the AB Testing add-on is active, you can configure JSONB targeting rules on a flag. Rules are evaluated by the server during evaluateAB. Supported operators include eq, in, gt, lt, and contains.

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Live updates

Flag changes pushed from the console are delivered to connected SDK clients within milliseconds via SSE. See Quickstart → Enable live updates.