Token Introspection
Token introspection is an OAuth 2.0 mechanism where a resource server asks the authorization server whether an opaque access token is active, which scopes it carries, and which subject it represents. The introspection endpoint returns a structured active or inactive verdict.
Technical Architecture & Deep-Dive
JWT access tokens can be verified locally with public keys, but opaque tokens require a call to the issuer. RFC 7662 standardizes introspection request and response fields, including `active`, `scope`, and `exp`.
Gateways may introspect at the edge before forwarding traffic. Cache introspection responses briefly to reduce latency, but respect short TTLs so revoked tokens fail fast. Never expose introspection credentials to browsers.
Key Architectural Benefits
Call an Introspection Endpoint
const res = await fetch('https://auth.example.com/oauth/introspect', {
method: 'POST',
headers: {
'Content-Type': 'application/x-www-form-urlencoded',
Authorization: 'Basic ' + btoa(clientId + ':' + clientSecret),
},
body: new URLSearchParams({ token: accessToken }),
});
const body = await res.json();
if (!body.active) return new Response('Unauthorized', { status: 401 });Implement Token Introspection at the Edge
Deploy lightweight API aggregation, edge caching, and secret injection in minutes without Docker containers or complex servers.
Frequently Asked Questions
Q:Should I introspect every JWT on every request?
Usually no. Local JWT signature verification is faster. Use introspection for opaque tokens or when you need immediate revocation beyond short JWT lifetimes.
Related Architecture Concepts
An access token is a credential that authorizes calls to a protected API on behalf of a user or application. OAuth providers issue access tokens with a limited lifetime and scopes. APIs validate the token signature or call an introspection endpoint before executing the request.
OAuth 2.0 is an authorization framework that lets an application obtain limited access to a user account on another service without handling the user password. The user approves requested scopes, and the application receives an access token it uses to call the service API.
A JSON Web Token (JWT) is a compact, URL-safe token containing a JSON payload of claims, such as user ID and expiration, signed by the issuer. Servers verify the signature to trust the claims without a database lookup, enabling stateless authentication.
A refresh token is a long-lived OAuth credential used only to obtain new access tokens without asking the user to sign in again. Refresh tokens are highly sensitive: anyone who steals one can mint fresh access tokens until the refresh token is revoked or expires.
Ready-to-Use Edge Recipes
To solve call clerk backend api from client side, never execute unauthenticated requests or embed private tokens directly in client bundles. RealComposer acts as a sub-10ms edge gateway running on Cloudflare Workers that securely injects credentials from your Secret Vault, normalizes responses, and prevents unauthorized API usage. Route calls through your RealComposer edge URL to guarantee complete privacy, robust origin validation, and low mobile latency.
To combine firebase auth user with supabase profile endpoint, use one RealComposer pipeline with parallel steps. Firebase ID token lookup and Supabase profile row merged at edge. Your React / Flutter / Mobile app makes one request instead of several sequential upstream calls.
To stitch firebase with clerk session bootstrap, use one RealComposer pipeline with parallel steps. Clerk session and Firebase FCM registration merged at startup. Your React Native app makes one request instead of several sequential upstream calls.