29 September 2025 · Isolde Venn
The first fourteen days of instrumentation debt
A new application, in its opening sprint, logs whatever the SDK made easy. Screen views, session starts, a purchase event copied from a tutorial. Two years later a product trio sits in Plot Room pretending they chose that geology. They did not. They inherited a fortnight of haste.
Instrumentation debt is not the absence of events. It is the presence of events that cannot be spoken as behaviours, plus the absence of an identity policy. The first is noisy. The second is silent and worse. Without a seam decision, every later cohort is a maybe. United Kingdom startups are especially prone to postponing identity because login is “a later milestone.” Later, the historic curves cannot be stitched, and the board is shown a D7 that only exists for the logged-in minority.
The house advice for a team still in those fourteen days is unfashionable: log fewer things, name them as verbs, write one paragraph on what you will not count as active, and refuse to print activation until a person could fail it. You will look under-instrumented in the first all-hands. You will look like adults in the third year.
If you are already past the fortnight, Grid Instrumentation is largely an archaeology course. We do not shame the first engineer. We do make you read the original commit messages, when they exist, so the debt has authors instead of weather.