Their order system goes down for four hours a week and cannot be changed. Design the queue that sits between it and your pipeline.

Every integration lesson assumes a queue and nobody designs one. Ordering per entity rather than globally, a dead letter path somebody actually reads, and what your pipeline does when the consumer is slower than the producer for four hours.

Updated Sep 2026 · Grounded in real Forward Deployed Engineer interview loops and written to a senior-engineer editorial bar.

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UP NEXT ON YOUR JOURNEY

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FEDITOR'S NOTE

The senior signal is treating the queue as a contract rather than a buffer: what it guarantees about ordering and delivery, and what it explicitly does not. The reserve probe is backpressure, because most candidates design the happy path and then say the queue absorbs the spike without saying what happens when it does not drain. Strong answers scope ordering per entity rather than globally, and they treat the dead letter queue as a workflow with an owner rather than a table. Watch for exactly-once claims, and for anyone whose retry design has no poison-message escape.

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