From Research Engineer to Principal Scientist: Santiago Cuéllar’s Galois Journey

When Santiago Cuéllar was an undergraduate studying mathematics at MIT, he thought he knew exactly how his career would unfold.

“I always thought I was going to be a professor of mathematics,” he said.

But there was one problem: every summer, while his friends were pursuing internships aligned with their long-term career plans, Santiago kept chasing whatever opportunities seemed most interesting. Again and again, those interesting opportunities turned out to be computer science internships.

“I didn’t think about my future very much,” he laughed. “I was just looking for cool stuff to do. By the time I graduated, I looked at my CV and realized: ‘Oh, I guess I like computer science!’”

In search of a way to combine his dual interests, Santiago found his way to formal methods—using mathematics to prove that software behaves correctly. He was hooked.

Finding the Bigger Questions

As a PhD student—this time studying computer science at Princeton—Santiago became deeply immersed in formal verification research. His plan was still to become a professor, but then he came face to face with the realities of academia.

“I spent six years proving one program correct,” he said. “I was the world’s foremost expert in this program, having spent so much time thinking about it, but I realized it wasn’t sustainable. Spending six years on one program is not something you can do in the real world.” 

The experience didn’t diminish his belief in the power of formal methods. If anything, it strengthened it. But it changed the questions he wanted to ask, shifting his interest from theory to impact and how formal methods could be used to solve real-world problems. 

Those questions eventually led him to Galois.

The Freedom to Follow Your Curiosity

When Santiago joined Galois as a Research Engineer in 2020, he wasn’t looking to become a Principal Scientist. He was looking to learn. 

Over the next few years, he worked across a broad range of disciplines: zero-knowledge proofs, cryptography, compilers, model-based systems engineering, program analysis, and more. For someone grounded in mathematics and trained in the hyper-focused world of academia, the experience was transformative. 

“I wasn’t trained as an engineer,” he explained. “I had to learn what it means to do good, sustainable work. Caring not just about whether something is technically correct, but how it fits into the bigger picture—what impact it has, how clients use it, and why it matters.”

He also found that Galois was a place where he could lean into many areas that he cared about – from the technical to the business side to the everyday tasks that keep an office running. He pitched in with recruiting and organizing events, joined the Jedi Council (our name for the engineering leadership team), unloaded the dishwasher, ordered groceries, stepped into technical leadership roles on projects, and even set out on a quest to find and source the best coffee for the office. 

“From the very beginning, Galois tells you that you have freedom to pursue what interests you,” Santiago said. “And it’s true!”

When he first mentioned that he might be interested in becoming a Principal Scientist, a colleague offered a surprisingly simple piece of advice: “The way you do that at Galois is you just tell people.”

Not long afterward, an opportunity appeared. The team was swamped preparing multiple proposal submissions, and needed someone to take ownership of one.

“They basically said: ‘Here’s one for you. Do it,’” said Santiago. “I was like, ‘are you kidding me?’ And they said: ‘You can drop it if you don’t want to do it, but here’s your opportunity.’”

“It was like being dropped into the deep end of a pool,” he added. “If you’re excited about it, it’s fun to figure out how to swim.”

‍From Solving Problems to Shaping Science

In 2025, five years after joining Galois, Santiago became a Principal Scientist. 

For him, the most exciting thing about that transition wasn’t the title, it was the opportunity to help shape the future of research.

As a Research Engineer, Santiago spent much of his time helping solve hard technical problems. As a Principal Scientist, he gets to ask a different set of questions: Which problems matter most? Where should the field go next? What new ideas are worth pursuing?”

Today, Santiago leads proposals, develops new research directions, and works at the intersection of mathematics, computer science, and emerging technologies. But he sees his journey as less a story about career progression and more a story about following one’s curiosity.

“The thing about Galois is that people are always willing to give you a chance,” he said. “Then you just have to prove yourself. I think that’s something you rarely find, but here, it’s just the way we do things.”