Define the North Star metric for Connect serving SaaS companies

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.

You are evaluating Stripe Connect for SaaS companies that embed payments and financial workflows into their own products. These platforms may use Connect to onboard their customers as merchants, route payments, handle payouts, manage compliance, reduce fraud, and support merchant growth across geographies and business models.

The interview focuses on how you would define a North Star metric for this segment. Your task is not just to name a metric, but to clarify what customer value Connect creates for SaaS platforms and their downstream merchants, how that value should be measured, and how the metric would help Stripe make product, growth, reliability, and platform investment decisions.

Assume the product serves a range of SaaS platforms, from vertical software providers to marketplaces and business tools that monetize through payments. The metric should be meaningful across this segment while still being precise enough to instrument, track, and act on.

The experience should consider:

- The primary users and stakeholders: SaaS platforms, their merchants, end customers, and Stripe internal teams.

- The value exchange Connect enables, including onboarding, payment acceptance, payouts, compliance, fraud management, and merchant growth.

- A clear metric definition, including numerator, denominator, time window, and whether the metric is volume-based, account-based, activity-based, or outcome-based.

- Instrumentation needs across platform integration, merchant onboarding, payment processing, payout completion, disputes, and retention.

- Relevant cohorts such as new vs. mature SaaS platforms, platform size, geography, industry vertical, integration type, and merchant lifecycle stage.

- Guardrail metrics for reliability, failed payments, onboarding drop-off, fraud, disputes, compliance failures, support burden, and platform or merchant churn.

- How the metric would inform product decisions without over-optimizing for revenue, payment volume, or growth at the expense of merchant trust and financial reliability.

Your goal is to propose a well-reasoned North Star metric framework for Stripe Connect serving SaaS companies, explain why it reflects durable customer value, and describe how Stripe should use it alongside supporting and guardrail metrics to guide decisions.