Add a Custom Cache

This guide shows how to cache validated access token claims to avoid re-validating the same token on every request.

When to use caching

Use caching when:

You receive multiple requests with the same access token
Token validation adds noticeable latency (especially with introspection)
You want to reduce the number of requests to the OIDC provider

Before you begin

This guide assumes you've completed the installation guide.

You should already have:

An Express project
The @monocloud/backend-node SDK installed
Environment variables configured in .env

Implement the ICache interface

The SDK accepts any cache that implements the ICache interface.

In-memory cache

src/cache.ts

import type { AccessTokenClaims, ICache } from "@monocloud/backend-node/express";

const store = new Map<string, { claims: AccessTokenClaims; expiresAt: number }>();

export const cache: ICache = {
  async set(token: string, claims: AccessTokenClaims, expiresAt: number): Promise<void> {
    store.set(token, { claims, expiresAt });
  },

  async get(token: string): Promise<AccessTokenClaims | null> {
    const entry = store.get(token);

    if (!entry) {
      return null;
    }

    if (Date.now() >= entry.expiresAt * 1000) {
      store.delete(token);
      return null;
    }

    return entry.claims;
  },

  async delete(token: string): Promise<void> {
    store.delete(token);
  },
};

How the interface works:

set(token, claims, expiresAt) — stores validated claims. expiresAt is the access token expiry time as a Unix epoch timestamp in seconds.
get(token) — retrieves cached claims, or returns null if the entry does not exist or has expired.
delete(token) — removes an entry from the cache.

Use the cache with protectApi()

Pass the cache to protectApi() through the options:

src/server.ts

import "dotenv/config";
import express from "express";
import {
  MonoCloudBackendNodeClient,
  protectApi,
  type AuthenticatedExpressRequest,
} from "@monocloud/backend-node/express";
import { cache } from "./cache";

const app = express();
app.use(express.json());

const client = new MonoCloudBackendNodeClient({ cache });

const protect = protectApi(client);

app.use(protect());

app.get("/api/data", (req, res) => {
  const { claims } = req as AuthenticatedExpressRequest;
  res.json({ claims });
});

app.listen(3000);

How it works: