Your first customers require obsessive, daily interaction to ensure the product works for them. Astronomer's founder spoke with their first managed Airflow customer four times a day for two months. This grueling process is essential for ironing out roadblocks and achieving product-market fit.

Eve knew they had product-market fit when customers found a bug that let them bypass invite restrictions. Users onboarded their entire firms months ahead of schedule, demonstrating an urgent, unmet need for the product.

Despite a clunky, multi-screen setup requiring users to copy and paste API tokens, 80% of early adopters completed the process. This incredible tolerance for friction was an undeniable signal that they were solving a desperate need in the market.

Product-market fit isn't just growth; it's an extreme market pull where customers buy your product despite its imperfections. The ultimate signal is when deals close quickly and repeatedly, with users happily ignoring missing features because the core value proposition is so urgent and compelling.

Initially, customers often "round down," focusing on missing features. A key sign of product-market fit is when they start "rounding up"—their faces light up in demos, and they imagine the product's future potential, forgiving current limitations because they believe in the core value.

Figma's CEO Dylan Field now realizes that a user sending a 14-page feedback document after a buggy, non-performant product demo was an unmistakable sign of strong demand. Intense engagement with a flawed product indicates a deep user need that founders should act on decisively.

Hux's founder measures success not just by retention, but by the passion of retained users. When users start writing in daily, angrily demanding bug fixes, it's a strong positive signal. It means the product has become so essential to their routine that they care deeply about its improvement.

In the early days, Canary's pitch received mixed reactions. However, the strong, visceral "I need this now" response from a few customers was a more valuable signal of product-market fit than getting a polite "that's cool" from everyone. This validates the "10 true fans" principle in B2B.

After experiencing numerous lukewarm responses to failed ideas, the intense, urgent demand from a customer for a successful product becomes an undeniable signal. The contrast between a polite 'maybe later' and a frantic 'how do I get this now?' makes true product-market fit impossible to miss.