Spencer Burleigh

Constraints beat prompts for AI code

Coding with AI has an entropy problem

A few hours into coding with AI, a pattern shows up. The code looks clean. Abstractions make sense. Tests pass. And yet under concurrency, your rate limiter collapses because the counter isn’t atomic.

Here’s the formula nobody talks about: failure= error rate × variance

Coding with AI massively increases variance. Even if error rate stays constant (big if), failures scale dramatically with output. After a few hours, you have 200 files of mostly okay spaghetti code and an AI who responds to your prompts with things like:

What are the World’s Best Airports?

Airline route networks really fascinate me. Walking into one of the great airports of the world you can feel the reach of the place and the people who move through it.

S Tier

The handful of irreplaceable hubs that every airline wants to fly to:

Marginality: the Hidden Variable of Impact

Impact isn’t only moral philosophy. It’s also pragmatic.

It’s more fun. Building something singular is infinitely more satisfying than being cog #12,428 in someone else’s machine.

It’s better for your head. People who optimize only for money or status often end up restless. Someone else will always have more and when you finally stop optimizing for that, you don’t have much else to show for it.

It compounds. Impact tends to snowball. Choosing to work on something meaningful attracts better people, creates deeper conviction, and sustains you through harder problems.

How to Own a Commodity

Everyone says not to start a commodity business. But the truth is, the best businesses are commodity businesses that really own the commodity. The trick is to build a structural cost advantage in production, or differentiate the product enough for customers to no longer view it as a commodity.

Oil’s Financials are Falling Apart

Hydrocarbons borrow energy from the past

Set aside climate for a moment and ask a simpler question: is continued growth in energy use structurally viable?

The classic de-growth argument says “no” because most modern energy comes from hydrocarbons (oil, gas, coal). These are finite geologic windfalls, so we’re effectively living off photosynthesis from millions of years ago. As those reserves deplete, the claim goes, society must ratchet back to something closer to nature’s replenishment rate.

In the long run, this is a pretty good argument against hydrocarbons! We’ve probably used around 50% of accessible oil reserves and depletion raises extraction effort [1]. The more oil we pump, the more expensive the next marginal oil becomes [2].

Founder’s Guide to Executive Skills

Being a founder requires many skills. As your company grows these skills overlap with those of an executive. To this end I’ve really enjoyed and learned a lot from the following episodes of Tom Henschel’s executive coaching podcast The Look and Sound of Leadership among others.

Last updated January 2026

The Factory's Quote is the Product

Machine shops’ value prop has come unbundled

Shops historically offered a bundle of services to their customer around usually a single type of production process (eg laser cutting, bending, powder coating, etc). Since finding, evaluating, quoting, and scaling with a shop was very involved, customers were extremely sticky.

This is still the case for most large scale production. But the system didn’t work for everyone and a revolution has started. Small startups who just wanted to buy a 25 parts, hobbyists building project cars, and even engineers at big companies who needed parts the next day for their prototype were delayed, ignored, and overcharged by shops who could only process a few, highest priority requests at a time.

Companies serving these markets with the help of new technology have now started the irreversible unbundling of the machine shop ecosystem:

Gold Mines & Self-Terminating Business Models

The Scooby-Doo ladder magnate isn’t just a cartoon punch-line, he’s a warning label. For forty years, Silicon Valley has been trained to worship businesses that compound indefinitely: SaaS dashboards that bill monthly, network effects that snowball, and margins that expand with every extra user.

Deep-tech plays in larger markets than SaaS but by a very different rulebook. Many businesses look less like revenue compounders than process compounder [1] and the revenue you do have looks like a discovery of gold. Finding gold is rare and it’s not necessarily a given you can strike it twice.

Basic Capital's Big Idea: Bet Your Retirement on Interest Rates

I just saw a Tweet for how Basic Capital can help you 5x the size of your retirement portfolio by borrowing money.

There’s definitely a way to lose all your money.

But more importantly, Basic butchers the entire philosophy of investing for retirement.

Your Credit Score is Worth More than the Plane

The airline business is brutal. Your seat availability today depends on aircraft orders placed a decade ago. Your inventory — empty seats — expire the moment the gate closes. Everyone from the mechanics to pilots are unionized. And competitors offer virtually the same product. In 2024, every major US airline lost money flying passengers [1]. Good thing that flying planes isn’t how airlines actually make money.

Dancing with Missiles

I wrote this essay back in school after spending months interviewing veterans and poring over declassified mission logs from the squadron my grandfather flew 100+ missions with during the Vietnam War.

The Wild Weasels were the “first in, last out” volunteers who intentionally drew fire from surface-to-air missiles to protect the strike packages behind them. I’m still struck by how much their story says about courage, politics, and the uneasy art of fighting a limited war under the shadow of super-power escalation.

Delta Wings & Supersonic Dreams

I wrote the following essay as a school research project into the Cold-War race for civil supersonic flight. In those times, Concorde’s slender delta wing came to symbolize industrial ambition, national pride, and, ultimately, the crushing economics of the luxury high speed travel against the egalitarian jumbo jet.

The first supersonic age ended in defeat when Concorde retired in 2003, but a few months ago, Boom Supersonic’s XB-1 demonstrator began a new era. Built in a Colorado warehouse rather than a state-owned hangar, Boom built the first privately funded civil supersonic aircraft, and broke the sound barrier in the quietest way ever recorded.

The story that follows captures the drama of that first supersonic age; may it also offer context, and a bit of propulsion, as we watch the second one taxi toward the threshold.

Andrew Jackson’s Ghost at the Fed

As politicians on both side thunder about ending, auditing or increasing the President’s authority over the Federal Reserve, it’s easy to forget we’ve fought this war before. Nearly two centuries ago, Andrew Jackson’s populist crusade against Nicholas Biddle’s Congressionally chartered “Second Bank of the United States” toppled our nation’s monetary backbone and set the stage for the Panic of 1837.

Back in high school, I wrote an essay about Jackson’s crusade and how a victory against imagined financial tyrants can become a long defeat for everyone else:

Bad Startup Names

I generally believe that good startup (and product) names are short, fairly easy to remember / spell, somewhat distinctive, and you can buy the .com / .ai domain name. I’m also a sucker for things that rank first alphabetically. If you meet (most of) these criteria you get a 4/5.

Founder’s Guide to Working with Filipino VAs

We wrote this guide to compliment Spencer’s popular “Founder’s Guide to Hiring an Operations Team in the Philippines.” It draws upon our personal experiences and insights gleaned from working with talented VAs (virtual assistants) over many years (shoutout to Angeli, Karyn, Rio, and Shang!) as well as observations from other founders who have successfully built remote teams in the Philippines.

• Rio & Spencer

For a real-world example of the kinds of tasks you can delegate, see our list of 221 tasks you can give to a VA.

Founder’s Guide to Personal Finance

I wrote this guide to help founders navigate the uncertainties of their financial lives. Your startup and its shares will certainty be worth unimaginably large amounts of money at some point but for now there are bills to pay and tricky situations to navigate.

See you at IPO!

Updated January 2026

Traveler’s Guide to Vaccine-Maxing

This guide is for a mainly US (possibly Canadian) audience who travels to much less developed countries in (generally) Africa, Asia, and South America and wants to save thousands of dollars by getting their travel vaccines at Costco’s Pharmacy.

You should start thinking about this at least a month (maybe two) before you leave. Time gives you the option to use the much cheaper Costco instead of a last-minute travel clinic that will charge you 10x. If you’re planning to travel many many months in advance your primary care physician could also help you get these shots closer to Costco’s pricing.

Founder’s Guide to Credit Cards

I wrote this guide to help founders get the most from their business and personal spending. As a founder, money has always been tight, but setting up simple systems for my business and personal spending has allowed me to travel the world for free, reward employees, and reduce our company’s burn.

See you at the airport!

We Probably Won't Fight Wars over Water

Much has been said about how wars of the future will be fought over water. This is probably true, but the scope of the conflict seem like they will be considerably smaller.

Founder’s Guide to Hiring an Operations Team in the Philippines

I wrote this guide to help founders work with global talent (generally in the Philippines). At my last company (Rent the Backyard YC S19), we built an operations team of nearly 20 based in the Philippines. The team helped us with everything from payroll to sales proposals to procurement. The team helped extend my capabilities as a founder while extending the company’s runway and our chance of success.

The below methods are a combination of what’s worked for me and what I’ve seen others use.

Travel Difficulty Index: My Tiered List for English Only Americans

This is a list of the difficulty I perceive it to be to travel (as an English speaking American) to different parts of the world that I have been to or am familiar with.

These rankings are probably most useful if you haven’t done much international travel. There are a lot of pretty easy-to-visit places that are still very interesting, so you should probably start there. I wouldn’t advise going more than one level higher than you’ve been before unless you’re visiting a local friend.

Founder's Guide to Building a Second Brain

Founders spend their days putting out fires. Context switching is constant and it’s important to step back and make sure the tasks you’re doing continue to line up with your long-term strategy.

The best way I know of working through these challenges is to be in a clear headspace. Clear headspace facilitates focus and enables you to do your best work.

When you are worried about forgetting a task, insight, or other important piece of information you aren’t able to fully dedicate your brain’s resources to a task.

The solution as Tiago Forte’s book lays out is to build a “second brain” when you log projects that need to be done, areas you’re responsible for, resources you can quickly reference, and an archive to look back on.

This takes a bit of effort but once you’re set up you will be able to focus on tasks for longer and with greater cognitive levels. If this guide is helpful you should read Tiago’s book for more depth.

What happened to Pippin / Rent the Backyard

In 2018 I co-founded Pippin, a housing factory startup, and our backyard home (ADU) brand Rent the Backyard. Our goal was to use California’s new ADU laws to build a lot of homes quickly by helping homeowners make the most of their unused land. After 4 years, 10 homes built, and a $10m+ contracted revenue annual run rate, we announced that we’re shutting down.

Gramps

My great-grandfather died last week. He was just shy of 100 years old. Gramps lived up in Otis Maine — a few miles from Acadia National Park. When I was growing up, Gramps would often stay a few days with my family on trips to visit his sister. We’d walk down into the creek near my house and while my brother and I fished, Gramps would tell us stories about growing up in not-so-rural anymore Connecticut and carve us bows and arrows from saplings.

I wrote a piece back in high school that I planned to share on Gramps’ 100th birthday. He didn’t quite make it but he was ready to go.

Japan - So Many Nuggets

I spent a bit of the holiday season in Japan visiting friends and riding the Shinkansen (bullet train). There is a lot to like. From clean, sprawling, dense, and affordable cites, to strangers offering to help an oftentimes extremely lost Gaijin (foreigner).

Yet, I leave the Land of the Rising Sun with more conflicted thoughts than I have for my own home. Things are so familiar and so different. There is so much peace and so much chaos. There is so much hope and so much despair.

I am also accumulating quotes about things far faster than I am writing about them so I thought I’d grab ones about Japan and smoosh them all together in the hope I can simulate the same conflict I feel as I depart.

Delta - Be Better

Airlines and their routes are fun because the decision to fly a plane from one city to another can be made from more than just an immediate profit seeking perspective.

Sukuk - No Interest Here

I just arrived back in Pittsburgh after spending a week at Carnegie Mellon’s campus in Doha, Qatar. My time on Doha was incredible and something I’ll very much be digesting over the coming weeks and may write about soon on this blog. I wanted to thank all of the students at CMU-Q for their hospitality (I had heard much about Arab hospitality and was still blown away by the generosity and kindness I was afforded) and for the administrators at CMU (Kevn D’Arco, Elizabeth Coder, Lenny Chan, and especially Renee Camerlengo) for all the work they did in to make this trip possible. They enabled our two groups and all the others who we interacted with to see the world as a smaller, more similar, place. I also wanted to thank my CMU-Q partner Rameez who got excited when I told him I had a blog and has definitely read more of these posts than my mother :p

Pierogis - with Bryndza Sheep Cheese

I know Slovakians speak Slovak. I just found it really interesting that in Bratislava – less than two miles from the border with Austria that English was the language of choice after Slovak (for both the waiter and the menu). This interest is perhaps misguided and it’s entirely reasonable for former countries of the Eastern Block to speak languages (Czech, Polish, etc) reflective of their history behind the Iron Curtain but it’s been nearly 30 years and Slovakia makes an exceedingly large number of (mainly German) cars.

Chicken - Inconsistent with the UK's Brand

I’ve become convinced British Prime Minister Theresa May is playing chicken.

The other day, the Tories (Conservative) held their party conference where May declared an end to austerity, called for a softer Brexit and declared that “there are better days ahead.” I fundamentally don’t understand how this can be true given the mindset of its leaders across both parties, an ugly superiority complex fundamental to national identity that the country has failed to shake since the dissolution of the Empire, and a general failure to grow.

Institutions, Institutions, Institutions

Snap - When your Core Competency is a Loss Leader

I’m increasingly receptive to the narrative that Snap is becoming the new Twitter. While the revenue of both are restrained by the limited degree to which they have information in the user (and such can’t charge advertisers a premium for really direct targeting like Google and Facebook), Snap also suffers from the lack of a feed users can be sucked into.

Melting Pots - Not Quite Everywhere

This term I’m taking a class on Chinese History since the Qing Dynasty. Our first reading was from Naomi Standen’s book “Demystifying China and I think the first chapter is one of the best introductions I’ve seen to Chinese History and the mindset of its current leaders.

The Saudi Spat with Canada - Messy

Kind of continuing from last week’s theme about authoritarianism, the Saudis are demonstrating how liberalization requires harsh stances to be taken to prevent a slippery slope away from government control. [1]

Protest in the 21st Century - Harder

I study Statistics and Machine Learning. Most of the time it’s really exciting to be so close to the frontier, but sometimes it’s terrifying because you understand how (relatively) easy it will be for totalitarian regimes to apply really powerful open-source software to do things like track their entire populations and automatically predict who might act out.

Remembering - Looking Forward

I’m in Germany this week and the Airbnb we’re staying at in Berlin overlooks the Memorial to the Murdered Jews of Europe. I was born in this country (in a little town called Wremen at the base of the Jutland Peninsula right on the North Sea) and while not a dual citizen, have always felt a connection to this place.

With that being said, I think it’s important to acknowledge the genocide the Nazis perpetrated here during the late 1930s/1940s.

~17 Million people died.

~6 million of them Jews.

I think it’s important to give space to the stories of those who died - either in concentration camps as a persecuted minority or as those fighting the tyranny against their fellow citizens.

Storytelling and Hope - Everywhere in Life

Success Bias Reply - Maybe the Opposite

Apollo - Success Bias

21st Century Moats - Your Brand

The numbers are clear though. As the article notes, half of Harley Davidson’s revenues come from deals to license their name and the sale of apparel. This is the power of branding — something apparel companies do particularly well (Vineyard Vines, Carhartt, etc) but they all do it — so the comparative gains to be had are probably minimal. Harley Davidson has probably found such success because Suzuki and its competitors don’t do this on the same level or at all.

Duty - A Definition

WH Auden’s The Unknown Citizen is a cynical response to perceived bureaucratic encroach by western governments in the 1930s so this is admittedly a pretty odd poem to write a July 4th post about but I found it odd that my residential advisor would post it in the hall [1] of my dorm freshman year so here we are. For some reason, these middling stanzas have stuck with me as a good definition of doing your duty to country.

Photos - Ubiquitous, Worthless?

Snapchat fundamentally changed the way we think about what a camera is. This is perhaps the natural conclusion of the spread in accessibly and volume of images in the last hundred years. First were the formal portraits you sat for once that your family framed and kept on the mantle that your grandparents still have today. Equipment was expensive and you didn’t even take the photo yourself.

American Words - Still Everywhere

Unified Korea - An Ongoing Problem

I didn’t have a quote in mind with which to really start this blog and going from zero to one is tough, so I checked the front page of Wikipedia. Of course, the recent US - DPRK (North Korea) summit was at the top of the list and a search in my doc for Korea revealed this interesting manifestation of the 1953 armistice.

Getting Started

I spend a lot of my time reading. The Economist and its English wit is a favorite. TechCrunch somehow makes the show Silicon Valley funnier. And The New Yorker’s longer form articles and works of fiction are just so pretty. As my father knows from his quest through my 700+ email deep inbox [1] for an elusive Amazon security key when I left my phone in a taxi [2] the other week, I also subscribe to a large number of newsletters, personal blogs, and syndicated RSS feeds focused on everything from finance to cooking [3].