SDK

The chemistry of co-founder alignment Romain Sestier and Guillaume Lebedel did not start StackOne because of a white paper or a market analysis. They started it because they wanted to work together again. This reversal of the traditional startup narrative—where the "visionary idea" usually takes center stage—is the fundamental bedrock of their recent $20 million Series A success. Having known each other for a decade and weathered the storms of three different companies, including the acquisition of Yieldify by Publicis, they entered the venture arena with a base layer of trust that most founders spend years trying to manufacture. Finding a co-founder is not about an interview process; it is about shared history and battle-tested reliability. Sestier argues that the co-founder relationship is more important than the product or the space. If you do not have a decade of history to lean on, you must artificially create it through high-intensity side projects or consulting gigs. The goal is to see how your partner reacts under pressure before you have millions of dollars and dozens of employees on the line. At StackOne, this trust allowed them to move with a speed that GV and Workday Ventures found irresistible. Shifting the mindset for venture scale Building a venture-scale company requires a psychological pivot that many talented entrepreneurs never fully complete. Sestier credits a former mentor at Google for a piece of feedback that changed his trajectory: "You're dreaming too small." This is a common trap for founders who focus on building a "good" business instead of a market-dominating infrastructure. Venture capital is not just fuel; it is a commitment to a specific level of aggression and magnitude. Once you take the money, the chips are down, and you have to play for the billion-dollar outcome because everyone involved has already agreed to that vision. This mindset shift trickles down into every operational decision. It means hiring for "talent density" rather than just filling seats to meet headcount goals. Guillaume Lebedel emphasizes that in the early days, you are not just hiring for skill; you are hiring for a lack of ego. You need "doers" who can transition from writing code to talking to clients without feeling that certain tasks are beneath them. The moment the talent density drops, the founders lose control of the culture, and the venture-scale dream begins to dilute into a series of middle-management compromises. The discipline of founder-led sales Sales at the seed and Series A stage is not a clean, automated process. It is "dirty work." StackOne achieved its initial traction by doing things that do not scale—cold calling, leveraging personal networks, and obsessively following up with prospects. Romain Sestier views sales through a simple framework of packaging and process. The packaging is about identifying why a customer should change their status quo right now. The process is about making it physically and legally easy for them to buy. One of the most dangerous traps for early-stage SaaS companies is "revenue at all costs." Sestier warns against selling to the wrong customers, even if they are willing to pay. If a customer drags your product in a direction that deviates from your long-term vision, you must be disciplined enough to cut them loose. You want the right type of revenue—the kind that validates your core thesis and helps you build a repeatable motion. At StackOne, this meant focusing on the CTO as the primary buyer and ensuring the product offered immediate, high-trust infrastructure value. Engineering the internal champion In enterprise sales, your biggest obstacle is not your competitor; it is your customer's internal bureaucracy. Founders must learn to treat their internal champions as partners in a joint venture. This means doing the work for them. If a champion needs to present a business case to a CFO, the founder should be the one writing the memo and preparing the data. You are essentially saving their time and reducing their reputational risk. Guillaume Lebedel notes that being a developer-centric product adds another layer of complexity. You are selling an SDK or an API that other engineers will have to live with every day. This requires a level of transparency and documentation that goes beyond typical sales collateral. By reducing the friction for the end-user (the developer) while simultaneously arming the champion with the financial justification for the CFO, StackOne created a dual-track sales motion that accelerated their growth past the "friends and family" network. Maintaining agility in the Series A era With $20 million in the bank, the temptation is to build a massive, rigid hierarchy. StackOne is fighting to stay nimble. This requires a culture where everyone stays close to the customer, regardless of their title. Guillaume Lebedel insists that even his engineers attend events and speak with users. This keeps the feedback loop short and prevents the product from becoming a bloated collection of features that nobody asked for. Ultimately, the Series A is just the beginning of the next chapter. The capital provides the runway to take bigger shots and move faster, but the core principles remain the same: high talent density, low ego, and a relentless focus on solving a massive problem. As StackOne continues to build the universal integration layer for B2B SaaS, Sestier and Lebedel are proof that the strongest startups are built on the foundation of shared history and a refusal to dream small.