Brandon Sim and
the problem behind
the problem

Before Brandon Sim rang a bell in Times Square, he helped write software for looking at stars. The two activities have little in common as photo opportunities. One requires a crowd and a company name on a screen. The other requires deciding which details in a sequence of numbers deserve attention. His career becomes more interesting when you start with the second.

In 2015, Sim appeared among the authors of a paper introducing FATS, a Python library for analyzing time series. The researchers focused on astronomical light curves: measurements of how an object’s brightness changes over time. Their problem was practical. Large quantities of observations needed to become useful features that researchers could compare. Someone had to build the machinery between the raw numbers and the interesting question.

Nine years later, in March 2024, Sim rang the Nasdaq closing bell as president and chief executive of Astrana Health. He had taken that role in January, following earlier appointments in engineering, technology and operations. The distance between an astronomy paper and an executive office is considerable. Yet both chapters involve an unglamorous preliminary task: understanding how the pieces actually work.

The teacher gets an invitation

The early geography is Southern California. At Diamond Bar High School, Sim accumulated the sort of academic record that makes an ordinary school timetable look underemployed. By his senior year, he had taken 16 Advanced Placement and college courses. He captained the FIRST Robotics team and qualified for the American Invitational Mathematics Examination six times. In 2011, he became a U.S. Presidential Scholar.

The more revealing detail concerns someone else. Scholars could invite an inspiring teacher to the recognition events. Sim chose Angela Jensvold, his physics teacher. He had been her student for three years; she also advised the school’s science teams. Alongside the competitions and advanced coursework, the choice gives the story a person to remember rather than another certificate.

“I am humbled,” he said of the recognition. Later executive biographies have good reason to move briskly past adolescence. Here, the school years earn their space. A future operator was already participating in team competitions, studying quantitative subjects and crediting a teacher. That is a more useful beginning than imagining a teenager with a fully formed corporate destiny.

“I am humbled.”

Brandon Sim · Presidential Scholars recognition, 2011

A useful habit of looking up

Harvard followed. Sim earned a bachelor’s degree in statistics and physics, graduating magna cum laude with high honors, and a master’s degree in computer science and engineering. The combination matters because it spans the question and the instrument: how to reason about observations, and how to make a computer do something useful with them. His research publications show that combination at work.

FATS arrived on arXiv in May 2015. Its authors included Isadora Nun, Pavlos Protopapas, Ming Zhu, Rahul Dave, Nicolas Castro and Karim Pichara alongside Sim. The project brought together collaborators from computational science and astronomy, with a shared interest in making large collections of observations useful. The project offered reusable methods for turning changing measurements into features. A library gives other people a way to repeat an analysis without starting from an empty editor.

A second paper, published in The Astronomical Journal in September 2016, concerned outlier detection. Nun, Protopapas, Sim and Wesley Chen described a system combining five detection methods, with weights learned dynamically. The broad challenge is easy to appreciate: an unusual observation can be valuable, but a method can also be unusually wrong. Combining approaches gives researchers another way to decide what merits a closer look.

The papers do not explain every later business decision. They establish something narrower and more substantial: before his executive appointments, Sim had participated in technical work involving noisy data, reusable software and the difficulty of identifying a meaningful exception. Those are actual projects, with other people’s names beside his. They put actual methods, code and collaborators behind the phrase “technical background.”

The job titles arrive in quick succession

Sim’s résumé also includes cofounding Theratech and serving as its chief technology officer. From 2015 to 2019, he worked as a quantitative researcher at Citadel Securities. That four-year stretch places professional quantitative work between university and his arrival at the business he would eventually lead. It also gave him a professional setting in which quantitative analysis was the job itself, rather than a subject on an academic transcript.

In June 2019, he joined the organization then known as ApolloMed as a project manager. By September, he was interim chief technology officer. In February 2020, he became CTO and vice president of engineering. Interim shared responsibility for operations followed that May; the chief operating officer appointment followed in February 2021. In November 2021, he became co-chief executive.

That is a brisk sequence. It also has an important family context. Brandon is the son of Kenneth Sim, the company’s executive chairman. The relationship appears in corporate disclosures and belongs plainly in the account. So do Brandon’s degrees, research, previous employment and operating appointments. A biography becomes less useful when it edits away either the connection or the work.

The change in responsibilities is the interesting part of the chronology. An engineer can improve a particular tool. An operations executive has to concern himself with the surrounding process, including people who will never open the code. A chief executive must decide what the organization should attempt at all. Sim moved through those levels inside the same business, acquiring broader responsibility as he went.

The appointments also resist an easy shortcut in telling the story. Reading only the final title loses the intermediate jobs. Reading only the speed loses the expanding range of responsibilities. The chronology is worth following at its own pace, even when the promotions themselves arrived quickly.

On January 19, 2024, he became president and sole chief executive. Thomas Lam moved to the vice chairman role. The company adopted the Astrana name the following month, and Sim rang the Nasdaq closing bell on March 4. A new title, a new name, a very public ceremony: several clean milestones for a working life that had become considerably harder to summarize.

A builder’s choice of bookshelf

Asked for his favorite book in 2026, Sim chose Douglas Hofstadter’s Gödel, Escher, Bach: An Eternal Golden Braid. His favorite quotation was a Richard Feynman line linking understanding to the act of creation. These are his stated preferences, rather than a personality test administered at a distance. Still, they make a fitting pair beside the research papers and engineering roles.

There is an attractive severity to the Feynman line. It allows little credit for nodding intelligently while someone else explains the machine. Building something exposes the missing steps. Software is particularly good at this sort of embarrassment: a computer has never felt obliged to run a program merely because its author attended an excellent university.

Across his earlier jobs, the sequence is visible: quantitative education, collaborative research, software and increasingly broad operating responsibility. Read that way, the favorite quotation supplies a useful question for his executive chapter. What does an organization’s leader need to understand well enough to make it work?

“What I cannot create, I do not understand.”

Richard Feynman · Sim’s selected favorite quotation

The scale changes; the questions get harder

In a conversation with Frederik Mueller for the podcast Healthcare Ops Wave, Sim discussed the move from project management to executive leadership. The operating habits described around that interview were decidedly practical: regular reviews, attention to dashboards and feedback between teams. Such routines rarely appear in a celebratory photograph. They are easier to appreciate when an organization has become too complicated to run on personal memory.

Growth raises the stakes of those routines. Astrana reported revenue of approximately $3.18 billion for 2025, an increase of 56 percent from the previous year. That is a company result, rather than a personal score for its chief executive. It does, however, describe the size of the enterprise for which Sim now bears responsibility. The project manager’s problems have acquired many more people and a much larger denominator.

The next appointments offer a concrete view of his priorities. In July 2026, Astrana named Daniel Rothman to an enterprise leadership role and Vishal Gupta senior vice president of enterprise transformation. Their remits included growth, finance, operations and reporting. Bringing in leaders with those responsibilities is one way a chief executive builds capacity beyond his own technical reach.

In June, Sim had been named an EY Entrepreneur Of The Year Greater Los Angeles award winner. The recognition placed him among a regional group selected by independent judges. The award supplies another date for the timeline; it does not finish the story. There is still a business to organize after the congratulatory messages have stopped arriving.

The Nasdaq photograph catches a cheerful exception to all this procedural work. Sim stands among colleagues, confetti passing in front of their faces. It is a crowd picture, appropriately enough. His published research had collaborators. His school achievement had a teacher. His executive career has a family connection and a succession of colleagues with responsibilities of their own.

The thread running through these chapters is the work of making complex things intelligible enough to use. A light curve becomes a set of features. A technical job becomes an operating brief. A growing company needs people who can take responsibility for parts of it. Sim’s career gives that progression specific dates, names and artifacts. The bell is a memorable punctuation mark. The more demanding work is what fills the sentences around it.