Inside Google’s System for Coordinated A/B Testing Across Its Global Service Fleet
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Google's fleet-wide A/B testing system provides rare, deep insight into large-scale experimentation infrastructure.
Google's fleet-wide A/B experimentation system uses a centralized framework with a unified assignment layer supporting hierarchical allocation and deterministic bucketing to minimize interference across interconnected services. It emphasizes exposure logging to distinguish assigned from truly exposed populations, configuration propagation to serving systems for low-latency decisions, and guardrails to enforce traffic limits. The system integrates with analytics pipelines to evaluate impact across end-to-end user journeys, reducing operational overhead for product teams.