Daily CTR model training pipeline

Design an end-to-end training pipeline for a click-through-rate model that retrains daily on ~5B labeled impressions, must produce a reproducible, validated model artifact, and feed a daily-refreshed online predictor. Latency to production (data ready to model live) should be under 4 hours, and a bad model must never reach 100% of traffic. Cover data ingestion/labeling, the orchestration, validation gates, and how offline training stays consistent with online serving.