The Builder Who Came Back
He started with a whiteboard and a garage. Now he sits across the table from the next generation of founders at Y Combinator - asking the questions he wishes someone had asked him.
He shows up two days a week in Phoenix. Not because Phoenix is fun in August - it isn't - but because that's where the HVAC contractors are. That's where the customers are. And Charlie Warren built his entire company on the principle that you don't understand a customer from across a conference room.
Today, Warren is a Visiting Partner at Y Combinator. The title means something specific: he's not a managing director or a check-writer by trade. He's a founder who made it through - including the hard parts no one talks about - and returned to the room where it starts. He carries W19 batch experience, a $60M fundraise history, and a $26M acquisition exit in his back pocket, along with the lessons that don't make it into the press releases.
Convex, the company he co-founded with Blake Meulmester in 2017, built what nobody else thought to build: a map-based sales intelligence platform for commercial service businesses. HVAC contractors. Elevator maintenance crews. Fire safety companies. The workers who keep buildings alive. Their product, Atlas, let field sales teams see every commercial property around them, understand who owned it, and understand what service opportunities existed. It was a novel idea in a part of the economy that most software investors walked past without stopping.
Before Convex, Warren was a Research Associate at the Council on Foreign Relations studying energy policy. Before that, he was in Technology, Media, and Telecom at Goldman Sachs. Before that, he had a Harvard MPA in electricity market design and an MIT MBA in energy and entrepreneurship. And before all of that, he grew up in Detroit, in a family that worked in the wiring business.
The through-line is physical infrastructure. Wires. Buildings. Systems that hold the modern world up. Warren was always interested in who profits when those systems work - and who suffers when they don't.
The Convex exit tells a complicated story. The company raised $60M total - a $17M Series A from Emergence Capital in 2020, a $39M Series B co-led by Fifth Wall and GGV in 2021. Then ServiceTitan acquired it in April 2024 for approximately $26M. On paper, that math is uncomfortable. In practice, it describes what the venture landscape looked like for vertical SaaS between 2022 and 2024. Warren joined ServiceTitan as VP of Commercial and Construction Markets, taking the Convex product - and team - inside a larger machine built for the trades.
He's now at Y Combinator as a Visiting Partner, advising the current batch on what it actually looks like to take a company from a garage hypothesis to a real business with real customers who depend on you. That particular knowledge doesn't come from reading. It comes from those two days a week in Phoenix when the customers tell you something your product team won't.
Expected value is a powerful way to think through hard decisions.- Charlie Warren, Co-Founder & CEO, Convex
Detroit upbringing - Family in the wiring business. A very specific education in how physical infrastructure actually works, long before any MBA curriculum explained it.
A.B. Magna Cum Laude, Phi Beta Kappa - Bowdoin College. The foundation. The beginning of what would become an unusual collection of elite credentials.
MPA in Electricity Market Design & Energy Efficiency - Harvard University. Energy systems. Policy levers. The economics of making power grids work. An unusual path for a future SaaS founder.
MBA in Energy, Entrepreneurship & Finance - MIT Sloan. Where the energy interest met the startup orientation. Two worlds colliding productively.
Goldman Sachs, Associate - Technology, Media & Telecom. The markets education. Understanding how large capital flows make decisions, and what that means for the companies being evaluated.
Council on Foreign Relations - Research Associate in Energy. The intersection of geopolitics and energy systems. A vantage point on how physical infrastructure shapes national behavior.
Route (Co-Founder) - Distribution and logistics startup. The first company. Where the founder instincts were first tested against real market friction.
Convex founded with Blake Meulmester - bootstrapped from a garage for six months with one whiteboard. The bet: software could make sense of commercial property data in ways that would transform field sales for service businesses.
Y Combinator W19 Batch + Growth Program - Convex enters YC. The network, the pressure, the demo day. The beginning of institutional backing.
$17M Series A - Led by Emergence Capital. Participation from YC, 1984 Ventures, UP2398, and PlanGrid founders. Validation from investors who understood vertical software.
$39M Series B - Led by Fifth Wall, Emergence Capital, GGV. Total funding: $60M. 4x YoY growth. Customer base doubled. Team quadrupled. The acceleration moment.
YC Top Companies 2022 - Named one of Y Combinator's most successful portfolio companies. The signal that Convex had become a benchmark for vertical SaaS.
ServiceTitan acquires Convex - ~$26M, April 2024. Warren joins ServiceTitan as VP of Commercial & Construction Markets, overseeing Fire Life Safety and Commercial Roofing divisions.
Visiting Partner, Y Combinator - The arc completes. The founder who went through YC now mentors the founders going through YC. Section B Capital angel investing on the side. Vertical AI is the thesis.
The gap between $60M raised and $26M acquired tells a story about the 2022-2024 venture correction in vertical SaaS - and about the value of maintaining customer relationships and product-market fit through a market turn.
When Charlie Warren and Blake Meulmester started Convex, they didn't have a pitch deck and a war chest. They had a garage and a single whiteboard. They bootstrapped for six months. No product. No customers. Just the belief that commercial service businesses - HVAC, elevators, fire safety, solar - were being underserved by software in a fundamental way.
The insight was geographic. Every commercial building is a data object. It has an owner, a square footage, an age, a set of systems that need servicing. If you could map that data and put it in front of a field sales rep - overlay it on an actual map - you could transform how commercial service companies found new customers.
The product they built was called Atlas. The company was called Convex. And the rule Warren learned early was the one he now repeats to YC founders: always lead with outcomes over features. A customer doesn't want to know what your product does. They want to know what happens to their business when they use it.
He learned that from an HVAC contractor. Not from a business school case study.
Warren grew up in Detroit, which is not an accident. Detroit is a city defined by its relationship to physical manufacturing and physical infrastructure. His family was in the wiring business. Long before he understood software markets or venture capital, he understood what it looked like when physical systems fail and what it costs when the people who maintain those systems don't have the right tools.
That background shaped the Convex thesis. The commercial services industry - the businesses that maintain the HVAC in hospitals, the elevators in office towers, the fire suppression in restaurants - is enormous and largely invisible to most software investors. Warren saw it clearly because he'd grown up adjacent to it.
His graduate degrees in energy policy and his time at the Council on Foreign Relations might look like a detour from his eventual software startup story. They weren't. Energy systems are infrastructure systems. They require understanding physical assets at scale, predicting maintenance cycles, understanding who owns what and where. The intellectual framework Warren built studying electricity markets translated directly into understanding how commercial property data could be organized and monetized.
At Goldman Sachs, in the Technology, Media and Telecom group, he saw the other side: how capital evaluates companies. How decisions get made with incomplete information. What it looks like from the outside when a sector is being transformed by software. That perspective made him a more sophisticated founder - someone who could speak the investor language because he'd been in the investor seat.
The ServiceTitan acquisition is the kind of outcome that requires context. Convex raised $60M. It sold for approximately $26M. In isolation, that arithmetic looks bad. In context, it describes the experience of a large portion of venture-backed vertical SaaS companies that raised at 2021 multiples and then navigated the 2022-2024 correction without the revenue growth needed to justify those valuations.
Warren joined ServiceTitan as VP of Commercial and Construction Markets. That's not a ceremonial title - ServiceTitan is the dominant software platform for trades businesses, and integrating Convex's commercial intelligence into their platform was the strategic rationale for the deal. He now runs the Fire Life Safety and Commercial Roofing divisions.
The fact that he transitioned to YC as a Visiting Partner suggests the exit, whatever its financial specifics, didn't diminish his standing in the founder community. If anything, having navigated a difficult exit gracefully - maintaining the product, the team, and the relationships - is the kind of story that makes a mentor credible.
Visiting Partners at Y Combinator are typically founders with specific domain expertise who spend time with the current batch offering office hours, advice, and pattern matching. Warren's domain is vertical SaaS - specifically, how to build software for industries that don't look like typical tech customers. Commercial services, trades businesses, physical infrastructure industries.
He's also angel investing through Section B Capital, focused on pre-seed and seed vertical AI startups. The thesis connects: AI applied to vertical industries - the same markets where Convex operated - is the next wave. Warren is positioning at the intersection of that thesis and the YC pipeline.
His longer-term interest, which he's discussed publicly, is using business as a vehicle for social change. He's cited J-PAL - the research organization that uses randomized controlled trials to study poverty reduction - as an inspiration. The idea is that well-run companies, operating in the right markets, can do more good than most policy interventions. That's the kind of aspiration that sounds abstract until you realize he spent years studying energy policy at Harvard and knows exactly what policy interventions fail to accomplish.
Always lead with outcomes over features.- Charlie Warren's core sales lesson, learned from an HVAC contractor
He grew up adjacent to physical systems - wiring, energy, buildings. Most software founders think in abstractions. Warren thinks in pipes and buildings and the businesses that maintain them. That's not something you learn at MIT.
Goldman Sachs gave him the investor's view - how capital evaluates, what signals matter, what the spreadsheet actually measures. He walked into every fundraising conversation knowing what was happening on the other side of the table.
Convex's Atlas wasn't just data software. It was map software. Warren understood that physical businesses think geographically - in territories and routes and neighborhoods - in ways that most SaaS products ignore.
Two days a week in Phoenix. Staying close enough to hear what customers actually say, not what they say to your account managers. That discipline - maintaining direct contact with the customer even as a company scales - is rarer than it should be.
His years studying electricity market design at Harvard and energy geopolitics at the Council on Foreign Relations give him a systems-level view of how markets work - and fail. Most founders haven't thought about regulatory architecture. Warren has.
The hardest part of being a good advisor is having actually done it. Warren built a company, raised $60M, navigated a difficult exit, and came back to the room to help the next class. That credibility is specific and earned.
Unscripted with Charlie Warren (Convex) - building vertical SaaS for the commercial services industry