How to Test JWT Token Expiration & Axios Silent Refresh Race Conditions in React

Writing a silent token refresh flow in React or Next.js using Axios interceptors looks simple on paper:

1. When an API call returns 401 Unauthorized, catch the error.
2. Call POST /auth/refresh with your refresh token to get a fresh access token.
3. Retry the original failed request with the new Authorization: Bearer <token> header.

However, in real-world applications, race conditions break this:

• If a dashboard loads 6 API requests in parallel when the access token expires, all 6 requests fail with 401 simultaneously.
• If your interceptor fires 6 concurrent POST /auth/refresh requests with single-use refresh token rotation, the backend detects token reuse and invalidates the entire user session, logging the user out!

Playground API now provides an ultra-fast 5-Second JWT Expiration & Token Rotation Simulator!

1. Simulating 5-Second JWT Expiry

Request a short-lived token:

Response:

Wait 5 seconds, and any subsequent request returns 401 Unauthorized ("TokenExpiredError").

2. Implementing a Queue-Based Axios Interceptor

3. Interactive JWT Simulator Studio

Test concurrent requests, token rotation, and clock drift in the documentation:

👉 https://playground.nileslabs.com/docs/jwt-rotation

Conclusion

Test your authentication recovery logic without waiting hours for tokens to expire. Master silent token refresh with Playground API!