Applied Systems

The production plumbing that puts models in front of traffic: feature stores, serving paths, and the data systems that keep training and inference reading the same values under real load.

Explainers

• Design a Feature Store — A model needs the same number at 3am training time and at the 50-millisecond serving moment — the user's 7-day click count had better mean the same thing in both. Build up from every team hand-rolling features in their service to a dual store fed by one definition: a columnar offline store holding years of history for point-in-time-correct training, a key-value online store holding the latest vector for 50K QPS under 50ms p99. Train/serve skew, the time-travel join, streaming freshness, and drift — drawn, computed, and animated.