Two clocks
Halvard's nightly cut assigns the last hour of deliveries to the wrong day, but only some nights. One system stamps UTC, one Oslo local time, and the boundary moves twice a year. Find the seam, prove it with the data, and fix the cut.
- intermediate
- about 25 min
- 4 objectives
- par 9 steps
- Halvard Freight
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- Customer
- Halvard Freight (synthetic customer; every timestamp and record on this box is made up for the exercise)
- Situation
- Finance groups deliveries by their UTC delivery date. The nightly job uses the carrier's Oslo wall-clock date instead. Earlier samples missed the midnight boundary; the late-March sample exposes the offset change and mismatched counts.
- Your role
- You are the FDE on the Halvard engagement. You have the recorded deliveries, the cut job's config and code, and a dry-run of the cut.
- Goal
- Identify the event clock, convert the delivery instant using Europe/Oslo, and group by the UTC day finance requires.
- 1.Name the field that carries no offset (you commit to an answer)
- 2.Name what moved at the end of March (you commit to an answer)
- 3.Count the deliveries in the two files whose local day and UTC day differ (you commit to an answer)
- 4.Make the cut run in one clock and show the dry run stable across the change