Your time-series has missing days, breaking moving averages and forecasts. Fill the gaps with a date spine.
Days with zero events simply don't show up in an event table, so a 7-day average quietly averages the wrong 7 rows. A date spine makes the missing days explicit. Here is the pattern.
Updated Sep 2026 · Grounded in real GenAI, LLM, and AI/ML engineering interview loops and written to a senior-engineer editorial bar.
Days with zero events simply don't show up in an event table, so a 7-day average quietly averages the wrong 7 rows. A date spine makes the missing days explicit. Here is the pattern.
Lead with where the obvious approach breaks, because that is the judgment they are screening for — most candidates jump straight to the happy path and lose the room.
Then walk the failure back through the pipeline in order, naming the one metric the customer's exec sponsor actually cares about before you propose the fix.
