We present a comprehensive investment thesis for Klaviyo, positioning it as the operating system for independent e-commerce. It argues that Klaviyo emerged at a crucial inflection point in retail—the shift from aggregated commerce (like Amazon) to direct-to-consumer (D2C) brands, which needed tools to leverage their customer data. The document highlights Klaviyo's strategic innovation in redefining marketing from an expense to a measurable "owned revenue" engine, driven by its unique real-time data platform architecture rather than traditional email marketing tools. Ultimately, the text asserts that Klaviyo is creating and dominating a new category: the B2C CRM, distinguishing itself from existing B2B-focused or less comprehensive competitors, all underpinned by its capital-efficient growth model and visionary founders.