You must ingest from a customer source that ships nulls, duplicates, and surprise schema changes. Design defensive ingestion.
Pure FDE territory: the customer's data is always dirtier than scoped. The layered defense, contracts, quarantine, drift handling, and the alert-severity matrix that keeps you from crying wolf.
Updated Aug 2026 · Grounded in real Forward Deployed Engineer interview loops and written to a senior-engineer editorial bar.
Pure FDE territory: the customer's data is always dirtier than scoped. The layered defense, contracts, quarantine, drift handling, and the alert-severity matrix that keeps you from crying wolf.
Lead with where the obvious approach breaks, because that is the judgment they are screening for — most candidates jump straight to the happy path and lose the room.
Then walk the failure back through the pipeline in order, naming the one metric the customer's exec sponsor actually cares about before you propose the fix.
