You have built a new CVR (conversion rate) prediction model for an RTB bidding system at a DSP. Offline metrics improved (e.g., lower log loss and higher PR-AUC), but you must validate that the change improves business outcomes under real auction dynamics. Design an online evaluation and rollout plan. Include: 1) What primary and guardrail metrics you would monitor (e.g., CPA, ROAS, conversions, spend, win rate, latency). 2) An experimental design appropriate for RTB (A/B test vs shadow mode vs interleaving). Define the unit of randomization and how to avoid interference. 3) How you would handle budget constraints/pacing and non-stationarity during the test. 4) What failure modes you would watch for (e.g., calibration shifts, bidder feedback loops, overbidding) and what rollback/ramp-up strategy you would use.