---
title: Notification listeners
slug: feature-experimentation/docs/notification-listeners
docTags: 
createdAt: 2026-08-05T20:40:00.000Z
---

Notification listeners

- give you flexibility in implementing custom integrations with analytics providers.
- let you configure integrations by passing data to external services.
- work by triggering a callback function that you define.

## Use cases

The following are a few example use cases for notification listeners:

- Send data to an analytics service and report feature flag decision data. For example, report that user\_123 was assigned to variation A.
- Use SDK events to send alerts to data monitoring tools like [New Relic](https://newrelic.com) and [Datadog](https://www.datadoghq.com) to visualize how A/B tests affect service-level metrics.
- Pass all events to an external data tier, like a data warehouse, for additional processing and to use business intelligence tools.
- Re-initialize your SDK to retrieve updated feature flag configuration data for your business-critical features.

## Notification listeners

Notification listeners in Feature Experimentation work by triggering a callback function that you define and provide at runtime. The following methods or lifecycle events trigger notification listeners if you have implemented the listener:

- **Decide methods** – Invoke the [Decision notification listener](docId:1SxhU55rO2wftlNek4f5U) if the listener is enabled.
- **Track event method** – Invokes the [Track notification listener](docId\:PaUUiwg7zYOguMb_HrFGN) if the listener is enabled.

:::hint{type="warning"}
**Important**
This method does not call the track notification listener when the specified event key is invalid
:::

- **Event batch flushed** – Invokes the [Log event notification listener](docId\:Rz6q1E5AKATNdC2U0P6ZK) if the listener is enabled.
- **New datafile retrieved** – Invokes the [OptimizelyConfigUpdate notification listener](docId\:kxCtpOyxtIKRX841frN3f) if this listener is enabled.