# A daily orders aggregation works fine when nothing goes wrong Canonical URL: Domain: Pipeline Design ยท Difficulty: medium ## Problem A daily orders aggregation works fine when nothing goes wrong. Tonight at 3am the on-call engineer gets paged: the dashboard is empty. Stdout from the run scrolled past hours ago, no run identifier ties one log line to a specific run, and the only failure signal is a nonzero exit code nobody is watching. The section names five things a script lacks (run identity, durable visibility, failure signal, recovery, idempotent restart). Spot the operability gap by adding the operational shell on the canvas: a structured-log destination, a metric-store destination, a paging destination, and a heartbeat that lets on-call see the pipeline is making progress. ## Related - [All practice problems](https://datadriven.io/problems) - [Mock interview mode](https://datadriven.io/interview/a-daily-orders-aggregation-works-fine-when-nothing-goes-wron-9b8ca18c) - [System Design Interview Questions](https://datadriven.io/data-engineering-system-design) - [Data Engineering Interview Prep Guide](https://datadriven.io/data-engineer-interview-prep) - [Daily Challenge](https://datadriven.io/daily) --- Source: DataDriven (https://datadriven.io). 100% free data engineering interview prep. Live code execution against Postgres 16, Python 3.11, and Spark sandboxes. No paywall, no premium tier, no signup gate.