exactly once
Applied AI interview questions tagged exactly once, across every topic.
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Concepts behind "exactly once"
The curriculum that explains the ideas these questions test.
Foundational
Idempotency and Exactly-Once EffectsIn a distributed system, calls fail and get retried, so the same request can arrive more than once. Idempotency means processing a request twice has the same effect as processing it once, achieved with idempotency keys and deduplication. It is the foundation of safe retries: without it, a retried payment charges twice or a retried pipeline double-counts. Applied-AI interviews probe it because LLM/data pipelines are full of flaky, retried steps, and 'exactly-once' is really 'at-least-once delivery plus idempotent processing'.⚙️ System Design for AI in Production
Core
Idempotent Data PipelinesData pipelines fail and get rerun, so a pipeline must be idempotent: rerunning it produces the same result, not duplicated or corrupted data. You achieve it with insert-overwrite by partition, MERGE/upsert keyed on a business id, and deterministic transforms, rather than blind appends that double-count on retry. Applied-AI interviews probe it because flaky pipelines are the norm, and a non-idempotent pipeline turns a routine retry into duplicated revenue numbers or a corrupted table.🗄️ Data & SQL EngineeringSign in