How would you detect unhealthy growth in Billing

Problem Statement Description

Product context: Stripe is financial infrastructure for internet businesses; its products include payments, Checkout, Billing, Connect, Radar, Issuing, Terminal, and tax tools.

Stripe Billing helps startups create subscriptions, invoice customers, collect recurring payments, manage retries, and grow revenue without building billing infrastructure themselves. In this interview, you are asked to define how you would detect “unhealthy growth” in Billing: growth that may look positive at the top level but is driven by low-quality, risky, unsustainable, or operationally problematic usage.

Assume Billing is seeing increased adoption among startups, with more merchants, invoices, subscriptions, and payment volume flowing through the product. Your task is to design a metrics approach that distinguishes healthy merchant and revenue expansion from growth that could create churn, payment failures, fraud risk, compliance issues, support burden, or poor end-customer experiences.

Focus on how you would define the right metrics, segment the data, instrument the product and payment lifecycle, and make the metrics useful for product, risk, support, and go-to-market teams. You do not need to propose a full product roadmap; the emphasis is on measurement quality and decision usefulness.

The experience should consider:

- What “growth” means for Stripe Billing, including merchants, subscriptions, invoices, payment volume, revenue, and retention

- How to define “unhealthy” growth using clear denominators, rates, and thresholds rather than only aggregate volume

- Startup-specific cohorts, such as new merchants, high-growth merchants, risky business models, geographies, pricing plans, and integration types

- Instrumentation across the billing workflow, including subscription creation, invoice generation, payment attempts, retries, disputes, refunds, cancellations, and support contacts

- Guardrail metrics related to failed payments, involuntary churn, disputes, fraud, chargebacks, compliance review, support load, and merchant/end-customer trust

- How to separate product problems from merchant mix changes, macro conditions, payment network issues, or seasonality

- How the metrics would support decisions such as deeper investigation, merchant education, risk intervention, product changes, or launch throttling

The goal is to show how you would build a practical metrics framework that helps Stripe identify when Billing’s apparent growth is creating hidden risk or degrading long-term merchant value, while still preserving the ability to support legitimate startup growth.