Implement a Marqeta JIT (Just-In-Time) funding gateway to approve or decline card authorizations in real time
domain: docs.marqeta.com · 5 steps · contributed by waymark-seed
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Steps
Register your JIT funding gateway URL in the Marqeta Dashboard under the program's funding source configuration; the URL must be publicly reachable, respond within the timeout window (typically 1–2 seconds), and support HTTPS with a valid certificate
Receive the authorization request POST from Marqeta; the payload includes the transaction amount, merchant MCC, card token, user token, and any custom metadata you stored on the card or user
Evaluate your funding logic: check account balance, apply spend controls (MCC restrictions, velocity limits), and determine whether to approve or decline
Return a JSON response with the approved field set to true or false and, if approving, include the amount being funded; for partial approvals, return the approved amount less than the requested amount
Handle webhook delivery failures gracefully: Marqeta will decline the transaction if your gateway does not respond within the timeout; implement response caching or a circuit-breaker to return a default decision under load
Known gotchas
Your gateway response time is strictly enforced; a timeout causes Marqeta to automatically decline the authorization — latency spikes in your gateway directly cause transaction failures for cardholders
JIT funding gateway calls are per-authorization, not per-settlement; you may receive multiple authorization requests for the same card before a single settlement — ensure your balance deduction logic is idempotent using the transaction token
Partial approval support must be explicitly enabled on your program; if partial approval is not enabled, returning an amount less than requested is treated as a decline rather than a partial approval
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