Field note · January 13, 2024
Cutting a lesson down — The anatomy of a silent failure
A walk through a real class of incident — the kind where every job is green, every test passes, and the number has been wrong for six weeks.
A note from writing The anatomy of a silent failure, which took three passes to get to something short.
A walk through a real class of incident — the kind where every job is green, every test passes, and the number has been wrong for six weeks.
The hard part of writing this was cutting it. The first version covered every case; the useful version covers the case you hit on a Tuesday and names the rest in a sentence. Completeness is a property of reference material, not of teaching material, and confusing the two produces something nobody finishes.
It sits in the Data quality and trust module. The exercise is a thinking one rather than a query one — some of this material is about deciding what to compute, and that does not need a keyboard.
Ordering matters here more than in most courses. It follows Testing data like you test code and leads into The first hour with an unfamiliar dataset, and reading it out of sequence mostly works but costs you the setup.
Free means free, and it also means we can rewrite it whenever it is wrong. No edition, no errata PDF, nothing to repurchase. The whole course is 36 lessons and the fixes land the day we find them.