How a Fintech Dev Built a Leak-Proof Expiring Quote Flow in React

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A frontend developer recently shared the architecture behind a timing-sensitive payout confirmation feature built for a fintech application. The flow required synchronizing user option selection, backend quote fetching, and expiry validation across multiple steps without stale or conflicting state. The engineer split responsibilities between TanStack Query, which handled server-mirrored data like quotes and fees, and Redux, which stored derived expiry timestamps needed independently across unrelated components. A custom React hook managed the countdown timer with strict interval cleanup to prevent memory leaks and stale closures. The design ensured that an expired quote could never be submitted at any stage by anchoring all expiry checks to a single epoch timestamp compared against the current time.

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