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The serverless SDK is a lightweight JavaScript SDK optimized for serverless environments while being compatible for any other platform/environment. This SDK harnesses the functionalities that all Statsig server SDK’s offer.
1

Install the Statsig SDK

npm install @statsig/serverless-client
2

Import the Statsig SDK

import {StatsigServerlessClient} from '@statsig/serverless-client'
3

Creating a StatsigServerlessClient instance

const client = new StatsigServerlessClient(process.env.STATSIG_KEY)
The client instantiation takes two arguments:
  • sdkKey : string This is your Statsig client API key. It is available from the Project Settings page in the Statsig Console. This is used to authenticate your requests.
  • options : StatsigOptions See here for more options.
4

Client Initialization

The following line initializes the client by loading feature gate and experiment configurations over network
const init = await client.initializeAsync();
5

Checking a Gate

const GateResult = client.checkGate('pass_gate', user);
This is a gate check in code.The checkGate method takes two arguments:
  • name : string The name of the Statsig gate that you are checking.
  • user : StatsigUser The Statsig user object for whom the gate is being checked. For more information on the user object, see here.
Refer to the Javascript on-device evaluation SDK documentation for how to check other entities like experiments and dynamic configs.
6

Logging an Event

client.logEvent('gate_check', { userID: randomUserId });
This is an event log in code.The logEvent method takes two parameters:
  • eventOrName : string | StatsigEvent This is the name and details of the event you are logging.
  • user : StatsigUser The Statsig user object for whom the event is being logged.
For more information on event logging, see here.
7
client.flush();
This flushes all events from the SDK to Statsig. Without this, you will not be able to get diagnostic information in the Statsig Console, nor any event data you logged.

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Putting it all together

index.js
import { StatsigServerlessClient } from '@statsig/serverless-client';

export default async function handler(request) {
    const client = new StatsigServerlessClient(process.env.STATSIG_KEY);
    
    let init = await client.initializeAsync();
    
    const user = { userID: Math.random().toString().substring(2, 5) };
    const passed = client.checkGate('pass_gate', user);
    
    client.logEvent('serverless_event', user, passed.toString());
    
    client.flush();

    return new Response(
      JSON.stringify({ passed, user }),
    );
}

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Bootstrapping

You can use the serverless SDK to bootstrap your client SDK. 
// Get client initialize response for a user
const values = statsig.getClientInitializeResponse(user, options);

// Pass values to a client SDK to initialize without a network request
For more information on bootstrapping including options and full code example, see here

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Bring your own CDN

The Statsig Serverless SDK also supports the bring-your-own-CDN model. You can now store your Statsig config specs anywhere, and initialize your client directly from that source. This use case has been tested and optimized for usage with AWS Lambda/Lambda@Edge and S3 but is compatible with any other data source. Ensure the URL you provide returns the Statsig config specs for your project. 
let init = await client.initializeViaURL("https://my-statsig-config.s3.us-east-1.amazonaws.com/my_dcs.json")
After initializing, use the SDK as usual.