Express.js

Create the cache once at module level and reuse it across every request.


import express from "express";
import { PlumaSnapshotCache } from "@pluma-flags/sdk";
 
const app = express();
 
// Create once; shared across all requests.
const flagCache = PlumaSnapshotCache.create({
  baseUrl: process.env.PLUMA_API_URL!,
  token: process.env.PLUMA_SDK_TOKEN!,
});
 
app.get("/dashboard", async (req, res) => {
  // req.user is set by your auth middleware (passport, JWT, etc.)
  const evaluator = await flagCache.evaluator({
    subjectKey: req.user?.id,
  });
 
  if (!evaluator.isEnabled("dashboard-v2")) {
    return res.redirect("/dashboard-legacy");
  }
 
  res.render("dashboard-v2");
});
 
app.listen(3000);

How it works

The subjectKey here is the authenticated user’s ID. Evaluation precedence for each flag:

Users on the deny list are always blocked (false).
Users on the allow list always get the flag (true).
Everyone else falls through to the rollout percentage or the base enabled state.

See Targeting & Caching for the full evaluation order and caching details.