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Client SDKs

Eppo supports a variety of client-side SDKs for different programming languages. To get started with a specific SDK, select the language below:

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JavaScript
Android Logo
Android
iOS Logo
iOS
React Native Logo
React Native
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Dart & Flutter

About​

Eppo's client SDK integrates with client-side applications that run on a user device. The below diagram shows how the SDK interacts with your application code, event tracking system, and Eppo's servers:

  1. Initialization: The SDK retrieves flag/experiment configurations from Eppo using an API key provided during initialization. The configuration data includes flag/experiment variations and traffic allocation. The SDK stores these configurations locally on the device for quick lookup during assignment.

  2. Assignment: Once the SDK is initialized, your application code invokes the SDK to assign a variation to a subject. This step does not involve any network requests.

  3. Logging (Experiments only): The SDK logs assignment events to whichever event tracking system you use (for example Segment) using a callback function you provide on SDK initialization. The assignment data includes information about the assigned variation and subject.

client-sdk-diagram

Globally Distributed Experiment Configurations​

The SDK retrieves experiment data from the globally distributed Fastly CDN. Each CDN location maintains a cache of experiment data. If there is a change to an experiment, such as an increase in traffic allocation, cached experiment configurations are updated within 10 seconds.

The SDK uses a background process to fetch and store the experiment data. The p75 latency of these requests is 50ms. This latency does not affect variation assignments, which use locally stored experiment data.