What guardrail metrics should Spotify track for Audiobooks at global scale

Problem Statement Description

Product context: Spotify is an audio streaming company; its products include music, podcasts, audiobooks, playlists, recommendations, creator tools, subscriptions, and ads.

Spotify has expanded beyond music and podcasts into audiobooks, creating a more complex global listening ecosystem for consumers, authors, publishers, narrators, and rights holders. As Audiobooks scale across markets, pricing models, catalog availability, subscription bundles, discovery surfaces, and creator economics may affect the broader Spotify experience in unexpected ways.

Your task is to define the guardrail metrics Spotify should monitor to ensure Audiobooks growth does not harm user trust, platform engagement, monetization, creator outcomes, or operational quality. This is a metrics interview question, so focus on how you would structure the measurement system rather than proposing product features or business strategy.

Consider that Audiobooks may compete with music and podcast listening time, introduce different consumption patterns, require rights and royalty tracking, and vary significantly by geography, language, catalog depth, and user intent. The metrics should be useful for decision-making at global scale, including launches, experiments, pricing changes, recommendation changes, and creator-facing program updates.

The metrics framework should consider:

- Clear definitions of each guardrail metric, including numerator, denominator, unit of measurement, and time window.

- Cohorts such as new vs. existing Spotify users, Premium vs. free users, audiobook listeners vs. non-listeners, creators/publishers, and country or language segments.

- Instrumentation needed across discovery, sampling, purchase or entitlement, playback, completion, refunds, royalties, and creator reporting.

- Guardrails for core Spotify health, including whether Audiobooks negatively affects music, podcasts, retention, satisfaction, or subscription behavior.

- Creator and rights-holder health, including whether audiobook partners receive reliable reporting, monetization, and audience development signals.

- Marketplace integrity and trust signals, including catalog quality, content availability, misleading recommendations, policy issues, and customer support burden.

- Experiment-readiness, including how guardrails would be monitored during phased rollouts, recommendation tests, pricing changes, or new audiobook access models.

- Decision usefulness, including thresholds, alerting, trade-offs, and how leadership should interpret metric movement across regions or user segments.

The goal is to present a rigorous guardrail measurement approach that helps Spotify scale Audiobooks responsibly while protecting the broader audio platform, user experience, and creator ecosystem.