Short write‑ups of problems we hit running a real commerce operation and what we changed in the code because of them. No product announcements; just the reasoning.
Every count, total and trend in aiku is precomputed — by ~650 small "hydrator" jobs that run at the point of change and a nightly sweep that catches what they missed, into ~150 stats tables and 35 partitioned time series at five frequencies. Why we chose that over computing on read, the bug where a single‑day redo flattened a whole month, and the index traps in partitioned tables.