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In this guide, we will walk you through how to leverage Statsig’s platform in serverless environments. The examples in this guide use the statsig-node SDK in a Google Cloud Function. These details shouldn’t matter - but you may have to adjust your implementation based on your cloud provider of choice.

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Usage

Statsig server SDKs can be used in serverless environments. If you are unable to initialize Statsig outside of a serverless function, you will incur a server round trip to Statsig servers to initialize the SDK in every function. After this point, all checks should be locally evaluated in the function. Finally, you’ll need to ensure any enqueued events (exposure and custom events) are flushed to Statsig prior to the function exiting. You’ll need to call statsig.flush() as demonstrated here using the Cloudflare flavor.

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Example

The following example has some debugging information built in to show the cost of initializing the SDK in a cloud function. In our experience, the initialize call takes less than a second, and subsequent function invocations should proceed without this startup cost. 
const statsig = require('statsig-node');

let requestsHandled = 0;
const initStart = Date.now();
let initEnd = 0;
let initialized = false;

const initializationPromise = statsig.initialize(process.env.sdkKey).then(() => {
  initEnd = Date.now();
  initialized = true;
});

exports.statsig = async (req, res) => {
  const functionStart = Date.now();
  requestsHandled++;

  if (!initialized) {
    await initializationPromise;
  }

  const alwaysOnGateValue = await statsig.checkGate({userID: 'gcp'}, 'always_on_gate');
  const functionEnd = Date.now();

  res.status(200).send({
    initStart,
    initEnd,
    functionStart,
    functionEnd,
    requestsHandled,
    initializeTime: initEnd - initStart,
    functionTime: functionEnd - functionStart,
    alwaysOnGateValue: alwaysOnGateValue,
  });
};
```javascript


### Alternatives

If this doesn't work for you, a custom integration may help but would require additional setup.

For example, you could create a background function which fetches your definitions from Statsig servers periodically, and stores them in your database.
Then, when initializing a Statsig server SDK, you can fetch the values from your database, rather than issuing a request to Statsig servers.

[Reach out to us in Slack](https://www.statsig.com/slack) if you want to talk through how to make Statsig play nicely with your architecture and requirements!

### Fastly Implementation

Depending on your Fastly account settings, you may have an extra layer of security enabled which requires a custom `fetch` method to be implemented for any network requests that need to be made to 3rd party domains. You must implement a custom `fetch` method that uses Fastly's required [backend parameter](https://js-compute-reference-docs.edgecompute.app/docs/globals/fetch).

To solve for this, first define a module in its own file that implements a global override of `fetch`:

```javascript
export { };

const ogFetch = fetch.bind(fetch.prototype);

globalThis.fetch = (input, init) => {
  const backend: string = input instanceof URL ? input.hostname :
    input instanceof Request ? new URL(input.url).hostname :
    new URL(input).hostname;

  const initWithBackend: typeof init = { ...init, backend };

  return ogFetch(input, initWithBackend);
}

(globalThis as any).EdgeRuntime = "fastly";
```javascript

Next, in the main function entrypoint, simply import the fetch override module prior to importing the Statsig SDK:

```javascript
import "./providers/utils/fastly-fetch-setup";
import Statsig from "statsig-node";