Token Refresh Race Conditions in Axios Interceptors: A Production Debugging Guide

Short summary

When multiple parallel API calls hit an expired JWT simultaneously, each failed request independently triggers a refresh-token call, causing a race condition that invalidates tokens and logs users out. The article walks through why standard Axios interceptor tutorials fail in production with React Query's concurrent fetches, and how a promise-queue lock mechanism can serialize refresh requests. It also covers subtle gotchas in error-detail checking that can still break the fix.

• •Parallel React Query fetches with expired JWTs cause simultaneous refresh-token calls that invalidate each other
• •Standard Axios interceptor patterns fail because token rotation invalidates prior tokens on each refresh
• •Solution: promise-queue lock mechanism to serialize refresh requests and retry queued calls

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