Jeff Levinsohn (opens in a new tab)
I have worked closely with Marcos Alvarez for more than four years at House Numbers. He was one of our first two non-founder engineering hires. When he joined, the engineering team consisted only of our CTO; Marcos and one other engineer were hired at the same time, and he has been instrumental in building nearly everything we've done since.
When Marcos joined, we barely had a product. Over the next four years, he helped us build two very different platforms essentially from the ground up, including our eventual pivot into an AI-enabled mortgage operations company. He's the definition of a versatile senior engineer: front end, back end, infrastructure, integrations, architecture, AI systems — whatever the problem requires, Marcos can usually go deep enough to figure it out.
One project that captures what he's particularly good at was building much of the communications infrastructure behind our mortgage platform. We needed to ingest email, SMS, phone calls, and voicemails; associate those communications with the correct loans; classify and interpret them; and make that context available to AI agents that could then take action. There wasn't much precedent for what we were doing and the requirements evolved constantly. Marcos researched the available tools and architectures, worked directly with our operations team to understand the real-world use cases, proposed approaches, built the system, and continued iterating on it as we learned.
That is very typical of how he works. Give Marcos a large, complicated problem with some ambiguity and he'll research it deeply, think through multiple approaches, ask for feedback, and then own it all the way through implementation and production. And if you give him a particularly nasty bug, he is like a dog with a bone — he genuinely seems to enjoy running it down until he understands exactly what's happening.
He's also incredibly reliable. Marcos has high standards, takes real pride in his work, communicates well, pushes back thoughtfully when he disagrees, and owns mistakes without ego. Over four years, I also watched him become a bigger part of our culture — still thoughtful and somewhat reserved, but with a playful sense of humor that became part of the personality of the team.
If I were starting another technology company tomorrow, Marcos is exactly the kind of engineer I'd want among the first few hires. He's experienced, versatile, thoughtful, technically excellent, and someone I trust to figure out hard things and build systems that last.