Node.js SDK

Node.js 22.5 or newer is required for node:sqlite. The SDK prefers optional better-sqlite3 and can fall back to node:sqlite.

@flagfix/node is the server SDK for APIs, workers, and SSR. It uses a server key and evaluate-all. Set apiHost to the FlagFix API. Never expose the server key to browsers.

import { createFlagFix, installShutdownHandlers } from "@flagfix/node";

const client = createFlagFix({
  serverKey: process.env.FLAGFIX_SERVER_KEY!,
  apiHost: process.env.FLAGFIX_API_HOST ?? "https://api.flagfix.io",
  storage: { mode: "persistent" },
});
installShutdownHandlers({ client });
await client.start();

withIdentity({ userId, anonymousId, traits }) returns a new client. Use it per request so concurrent users do not share one identity. exportFlagState() returns the current FlagState or null for React serverFlagState.

Defaults: evaluateMode: "server" (evaluate-all), SSE off, poll interval 0. Set flags.pollIntervalMs to poll. track accepts a string or { event, userId, properties }. An empty serverKey throws.