Course note — Monitoring data, not just jobs

Revised Monitoring data, not just jobs this week. The change was small and the reason was not.

Job monitoring tells you the code ran. Data monitoring tells you the numbers are right. Teams that only have the first find out about the second from a stakeholder.

The first draft explained the mechanism and stopped. What was missing was the failure: the thing that happens when you get it wrong, described concretely enough that someone recognises it later. A lesson that only teaches the correct version leaves you unable to spot the incorrect one, which is the situation you will actually be in.

It sits in the Shipping it and keeping it alive 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 Orchestration, and what "it runs every night" costs and leads into Owning something that runs without you, 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.