Simon Willison's Weblog: entrepreneurship

CoreWeave adds Marimo to their 2025 acquisition spree

2025-10-31T13:57:51+00:00

I don't usually cover startup acquisitions here, but this one feels relevant to several of my interests.

Marimo (previously) provide an open source (Apache 2 licensed) notebook tool for Python, with first-class support for an additional WebAssembly build plus an optional hosted service. It's effectively a reimagining of Jupyter notebooks as a reactive system, where cells automatically update based on changes to other cells - similar to how Observable JavaScript notebooks work.

The first public Marimo release was in January 2024 and the tool has "been in development since 2022" (source).

CoreWeave are a big player in the AI data center space. They started out as an Ethereum mining company in 2017, then pivoted to cloud computing infrastructure for AI companies after the 2018 cryptocurrency crash. They IPOd in March 2025 and today they operate more than 30 data centers worldwide and have announced a number of eye-wateringly sized deals with companies such as Cohere and OpenAI. I found their Wikipedia page very helpful.

They've also been on an acquisition spree this year, including:

Weights & Biases in March 2025 (deal closed in May), the AI training observability platform.
OpenPipe in September 2025 - a reinforcement learning platform, authors of the Agent Reinforcement Trainer Apache 2 licensed open source RL framework.
Monolith AI in October 2025, a UK-based AI model SaaS platform focused on AI for engineering and industrial manufacturing.
And now Marimo.

Marimo's own announcement emphasizes continued investment in that tool:

Marimo is joining CoreWeave. We’re continuing to build the open-source marimo notebook, while also leveling up molab with serious compute. Our long-term mission remains the same: to build the world’s best open-source programming environment for working with data.

marimo is, and always will be, free, open-source, and permissively licensed.

Give CoreWeave's buying spree only really started this year it's impossible to say how well these acquisitions are likely to play out - they haven't yet established a track record.

Via @marimo_io

Tags: entrepreneurship, open-source, python, startups, ai, jupyter, marimo

Fell in a hole, got out.

2025-07-16T18:36:31+00:00

Fell in a hole, got out.

This is an absolutely fascinating entrepreneurial war story by Medium CEO Tony Stubblebine, describing how they went from losing $2.6 million per month in 2022 to being monthly profitable since mid 2024.

By the middle of 2022, the readers were complaining that Medium was flooded with never ending get-rich-quick schemes and the founder (Ev) was complaining about clickbait and barely warmed over summaries of other people’s content. [...]

Because of the quality issues, it wasn’t just a matter of cutting costs because if that’s all we did we’d have a profitable business selling access to content that embarrassed us. That might look like business success, but we looked at it as a failure of mission and a way to waste our lives.

Fixing the business was hard. They ended up dropping from 250 to 77 people, breaking the lease (eventually) on a $145k/month office in San Francisco and, most importantly, pulling off a "recap" - a recapitalization, essentially a reset of the cap table.

I've never seen this process described before. Tony shares a lot of details on how it works, including these notes on how to get existing investors to agree to terms that will aggressively dilute their investment:

Mark Suster made the case that for relationship reasons with other investors, new investors don’t actually want to be the ones to force the recap. They’d rather you do it first and the way to do it is for management to threaten to quit. [...]

I can’t quite convey to you how far out of my depth that management-walks strategy is. It’s beyond just that I’ve never seen a recap before. I’m just not that aggressive that I could imagine putting an ultimatum to investors over more than $200M worth of investor rights. And yet, the logic is clear and I did eventually accept that without the recap Medium would fail in the future and my work in between would be for naught. [...]

In order to justify the recap, you have to make the case that you are clearing incentives for the go forward team. That means everyone’s past effort is getting crammed down and only go forward efforts are being rewarded.

Via Jason Kottke

Tags: entrepreneurship, medium

Quoting Paul Biggar

2025-06-16T17:56:57+00:00

In conversation with our investors and the board, we believed that the best way forward was to shut down the company [Dark, Inc], as it was clear that an 8 year old product with no traction was not going to attract new investment. In our discussions, we agreed that continuity of the product [Darklang] was in the best interest of the users and the community (and of both founders and investors, who do not enjoy being blamed for shutting down tools they can no longer afford to run), and we agreed that this could best be achieved by selling it to the employees.

— Paul Biggar, Goodbye Dark Inc. - Hello Darklang Inc.

Tags: entrepreneurship, programming-languages, startups

What does a board of directors do?

2024-12-12T22:15:43+00:00

What does a board of directors do?

Extremely useful guide to what life as a board member looks like for both for-profit and non-profit boards by Anil Dash, who has served on both.

Boards can range from a loosely connected group that assembled on occasion to indifferently rubber-stamp what an executive tells them, or they can be deeply and intrusively involved in an organization in a way that undermines leadership. Generally, they’re somewhere in between, acting as a resource that amplifies the capabilities and execution of the core team, and that mostly only helps out or steps in when asked to.

The section about the daily/monthly/quarterly/yearly responsibilities of board membership really helps explain the responsibilities of such a position in detail.

Don't miss the follow-up Q&A post.

Tags: anil-dash, entrepreneurship, governance

Quoting James Dillard

2024-11-23T18:47:53+00:00

If you try and tell people 5 interesting things about your product / company / cause, they’ll remember zero. If instead, you tell them just one, they’ll usually ask questions that lead them to the other things, and then they’ll remember all of them because it mattered to them at the moment they asked.

— James Dillard

Tags: entrepreneurship, startups

Quoting Craig Mazin

2023-12-31T20:53:21+00:00

There is something so vulnerable and frightening about doing your own thing, because it’s your fault if it doesn’t work. And then there’s this other kind of work, where you’re paid an extraordinary amount of money, you’re the hero before you walk in the door, you’re not even held that accountable, because you have a limited amount of time, and all you can do is make it better.

— Craig Mazin

Tags: entrepreneurship, startups, screen-writing

Reasons Why I Think 50% Coding 50% Marketing is the Best Framework for Solo Tech Founders

2022-10-08T15:43:09+00:00

Reasons Why I Think 50% Coding 50% Marketing is the Best Framework for Solo Tech Founders

Jon Yongfook offers a deliciously simple recipe for splitting up the work of both developing and marketing a product: one week of development, then one week of marketing, then repeat. I really like this concept: I mix the two activities randomly at the moment and constantly find myself feeling guilty that I’m not spending enough focused time on either of them!

Via @yongfook

Tags: entrepreneurship, marketing, startup

Retrospection and Learnings from Dgraph Labs

2022-09-16T18:43:34+00:00

Retrospection and Learnings from Dgraph Labs

I was excited about Dgraph as an interesting option in the graph database space. It didn’t work out, and founder Manish Rai Jain provides a thoughtful retrospective as to why, full of useful insights for other startup founders considering projects in a similar space.

Via Hacker News

Tags: entrepreneurship, startups, graphql

What's the first thing you would check if the company is losing money even though there's a big increase in its revenue?

2016-08-15T14:12:00+00:00

My answer to What's the first thing you would check if the company is losing money even though there's a big increase in its revenue? on Quora

The company's expenses.

Tags: business, entrepreneurship, startups, quora, careers

What are the key points accelerators such as Y-Combinator drill into their startups?

2014-02-07T18:36:00+00:00

My answer to What are the key points accelerators such as Y-Combinator drill into their startups? on Quora

Build something people want. This is so important that YC have it printed on the T-Shirts they hand out to each batch.

They also teach the importance of launching something and getting real feedback. The entire three month YC process is based around the need to launch and demonstrate traction in order to raise money from investors.

Paul Graham's essays cover many of the lessons that YC teaches startups.

Tags: entrepreneurship, funding, startups, y-combinator, quora

Do accelerators (which do not take up equity) accept not-for-profit ventures into their programs? If yes, which are some of the best ones?

2014-01-28T13:41:00+00:00

My answer to Do accelerators (which do not take up equity) accept not-for-profit ventures into their programs? If yes, which are some of the best ones? on Quora

Y Combinator recently started funding non-profits: http://ycombinator.com/np.html

Tags: entrepreneurship, funding, startups, y-combinator, quora, 500startups

What are some examples of startups funded simply for the strength and uniqueness of its founders rather than for any particular idea?

2013-12-15T13:52:00+00:00

My answer to What are some examples of startups funded simply for the strength and uniqueness of its founders rather than for any particular idea? on Quora

A good portion of YC companies fit this definition - it's common for YC to fund the team and then work with them to help them either fix their initial idea or find a better one.

Tags: entrepreneurship, funding, startups, y-combinator, quora

As a non-technical single founder for a web startup, is it better to hire a design firm to build the prototype, or find a technical co-founder?

2013-12-04T11:17:00+00:00

My answer to As a non-technical single founder for a web startup, is it better to hire a design firm to build the prototype, or find a technical co-founder? on Quora

Find a co-founder. The problem with using an outside agency to build your initial prototype is that you won't really start learning about your product until after you have launched it. You need to have the talent available in-house to then make changes and improvements based on the feedback you get from real users.

Don't put yourself in a position where you've spent all of your money on external development before you learn that you haven't built the right thing. Launching the prototype is just the start of your development process.

Tags: entrepreneurship, prototyping, startups, web-development, quora

I've been working alone for about a year, how do I get out of this feeling of loneliness because no one is around me?

2013-11-26T14:28:00+00:00

My answer to I've been working alone for about a year, how do I get out of this feeling of loneliness because no one is around me? on Quora

This is why co-working spaces exist. I don't know which country you are based in but here in the UK most cities and many larger towns now have at least one tech-focused co-working space where you can rent a desk on a month-to-month basis and have a work environment outside your home with other freelancers with whom you can socialize.

I used to frequent a co-working space in Brighton, UK which was a hive of activity, and great for business as the freelancers there were always sub-contracting to each other and forming temporary teams to get larger projects finished.

Tags: entrepreneurship, startups, web-development, quora, careers

Should I pull the plug?

2013-11-24T12:41:00+00:00

My answer to Should I pull the plug? on Quora

Is there any way if turning this in to a recurring revenue product? It's enormously easier to get money from an existing customer (since they already know that your product works for them and is worth the cash) than to sign up a brand new customer.

Building a business takes a long time. If you need 24 sales a week and you've only just made your first sale, it will take you months to get to your break-even point.

That gives you three options:

Give up
Raise money from investors
Find an alternative income source to support yourself

Based on what little information you've provided, it sounds like you should be looking at number 3. Plenty of successful businesses have been built by people as a side-project to their regular income.

Tags: entrepreneurship, startups, quora, leanstartups

In which case have you seen a non-tech sole founder rise to build a sustainable great company without a tech co-founder? How can this work? What are the steps/advice you would give to the non-tech founder?

2013-11-20T15:45:00+00:00

My answer to In which case have you seen a non-tech sole founder rise to build a sustainable great company without a tech co-founder? How can this work? What are the steps/advice you would give to the non-tech founder? on Quora

ZeroCater is my absolute favourite example of this. The solo founder, Arram Sabeti, started the company by running it manually using a spreadsheet. He only got a technical co-founder involved at the point when just running billing was taking him over 20 hours of manual work a week.

Here's a great write-up of his experience: From Selling Scoops Of Ice Cream To Founding ZeroCater | TechCrunch

Tags: entrepreneurship, funding, startups, quora

I'm a developer, I've an idea, how to look for funding?

2013-11-20T15:30:00+00:00

My answer to I'm a developer, I've an idea, how to look for funding? on Quora

If you only need $10,000-$15,000 you should be looking at funding it yourself - professional investors very rarely get involved for that size of raise, and you probably wouldn't want them to - giving up equity in exchange for so little money is usually a bad idea.

The exception is startup accelerators, which are often set up for exactly this kind of investment. Y Combinator, Techstars and so on would be worth considering.

Tags: entrepreneurship, funding, ideas, startups, quora, ios

What should be my strategy to become a tech entrepreneur?

2013-11-20T12:28:00+00:00

My answer to What should be my strategy to become a tech entrepreneur? on Quora

Go and work for an early-stage startup. Pick well and you'll learn a ridiculous amount in a very short space of time: excellent preparation for later striking out on your own.

Tags: business, entrepreneurship, startups, quora

Can top VCs hire almost any employee they want for their portfolio companies?

2013-11-07T15:50:00+00:00

My answer to Can top VCs hire almost any employee they want for their portfolio companies? on Quora

There's little a VC can do to convince someone to go and work for one of their portfolio companies that the company couldn't do itself. They might hear about good candidates through their networks, but that candidate will still have plenty of other opportunities to chose from.

VCs are often better positioned than their portfolio companies in helping to find candidates for senior executive roles, simply because early-stage companies are unlikely to have already made the kind of connections they'll need to fill those roles.

It's still up to the company to convince, evaluate and close the hire.

Tags: entrepreneurship, funding, startups, quora

Is it worth it to give up equity in a seed stage company for something other than money? E.g. access to multiple consultants/mentors, as well as regional angel and vc groups?

2013-11-06T14:34:00+00:00

My answer to Is it worth it to give up equity in a seed stage company for something other than money? E.g. access to multiple consultants/mentors, as well as regional angel and vc groups? on Quora

Yes, but not very much equity. It's reasonably common to give small (less than 1%) stock grants to members of your advisory board for example.

And of course you should be making stock option grants to your employees.

Tags: entrepreneurship, funding, startups, quora

Is it possible to run a successful company without being unethical or operating on the fringes of the law?

2013-10-30T13:16:00+00:00

My answer to Is it possible to run a successful company without being unethical or operating on the fringes of the law? on Quora

There is nothing inherently unethical about entrepreneurship. Find a problem people have. Figure out how much money solving it will save them (or help them make). Charge them less than that.

You certainly shouldn't need to do anything illegal - in fact operating within the law is a requirement if you want your company to be successful, attract high quality customers and raise money from investors.

Plenty of people have built ethical companies. Some people take unethical shortcuts, but it certainly isn't required.

Tags: business, entrepreneurship, ethics, law, startups, quora

What are most important websites, online sources of knowledge and news for startups?

2013-10-30T12:14:00+00:00

My answer to What are most important websites, online sources of knowledge and news for startups? on Quora

Hacker News is still the best starting point, which is pretty impressive considering how long the community has been around.

http://news.ycombinator.com/

Tags: entrepreneurship, startups, quora

What do you do when you passionately believe in what you're doing and have been seeing strong customer validation, but people around you constantly diss it? How do you persevere without a support system?

2013-10-23T16:30:00+00:00

My answer to What do you do when you passionately believe in what you're doing and have been seeing strong customer validation, but people around you constantly diss it? How do you persevere without a support system? on Quora

This is one of the reasons it's a good idea to build a circle if trust with other entrepreneurs - or potentially even move to a "startup hub" region where more people are doing startups.

Is there an entrepreneur-focused co-working space near you that you can join?

Likewise, consider attending high quality entrepreneur meetups (like the Hacker News meetups in London) - or even applying to a reputable startup accelerator.

Tags: entrepreneurship, psychology, startups, quora, lifehacks

What should the CEO's salary be in a startup seeking seed capital? Is there an average number?

2013-10-22T09:30:00+00:00

My answer to What should the CEO's salary be in a startup seeking seed capital? Is there an average number? on Quora

If you haven't yet raised any capital, how can you pay a CEO salary at all?

If you're asking about what you should tell your seed stage investors your salary will be, just go for something sensible that allows for an OK standard of living in your area. Your investors don't want you to be distracted by living in abject poverty so they won't mind you paying yourself something reasonable.

There's no harm in discussing your salary with them - they might even suggest pushing it up a little. It very much depends on how much you are raising, your personal situation (family, mortgage etc?) and where you are located.

Tags: entrepreneurship, funding, startups, quora

Why was the popular Silicon Valley incubator named Y Combinator?

2013-10-20T09:39:00+00:00

My answer to Why was the popular Silicon Valley incubator named Y Combinator? on Quora

From this interview with Paul Graham http://www.paulgraham.com/frinte...

"It's a function that builds recursive functions without them needing to have names. The Y Combinator is one of those things that seems miraculous when you first encounter it. You wouldn't necessarily have expected such a thing to be possible. We named the company after it partly because we thought it was such a cool concept, and partly as a secret signal to the kind of people we hoped would apply."

Tags: entrepreneurship, paul-graham, siliconvalley, startups, y-combinator, quora

What prevents founders from taking blown up salaries?

2013-10-19T17:11:00+00:00

My answer to What prevents founders from taking blown up salaries? on Quora

When the money runs out, the startup dies. If a founder takes a high salary they are reducing the runway of the company, and dramatically increasing its chance of failure. Good founders will take the lowest salary they can make work for them.

In response to your updated question: in the very specific scenario you describe where a dishonest founder manages to raise a large amount of money while maintaining enough control to be able to set their own salary, there is nothing to stop then from paying themselves a super high salary for a few years. This sometimes happens. But the startup world is small and runs on reputation, so they would find it difficult to fool investors like that again.

If they paid themselves a high salary but their company performed really well and the investors were happy with their return, then maybe they were worth the salary they set for themselves!

Tags: entrepreneurship, funding, startups, quora

I have an offer from an angel, but just landed a 5 minute meeting with a big time VC. Do I try use the offer from the angel to my advantage, if so, how?

2013-10-13T09:07:00+00:00

My answer to I have an offer from an angel, but just landed a 5 minute meeting with a big time VC. Do I try use the offer from the angel to my advantage, if so, how? on Quora

An offer is worth a lot more than a five minute meeting - and VCs are much more likely to take you seriously if you've already convinced someone else to invest.

Have you read Paul Graham's recent (Sept 2013) guide to fundraising? If not, go and read it and do what he says to do :) http://paulgraham.com/fr.html

Tags: entrepreneurship, funding, startups, quora

What are some early examples of SaaS?

2013-09-30T09:58:00+00:00

My answer to What are some early examples of SaaS? on Quora

37 Signals' Basecamp was one of the pioneers if modern SaaS back in 2004.

Tags: 37signals, enterprise, entrepreneurship, startups, quora, saas

What can startups do on big data day one?

2013-09-16T13:05:00+00:00

My answer to What can startups do on big data day one? on Quora

Log everything, and then forget about it. That way you'll have data you can analyse later on, but aside from setting up logging and log storage you won't waste any time messing around with Big Data when you haven't yet found product-market fit.

Tags: entrepreneurship, startups, quora, big-data

How can I sell an idea to investors?

2013-09-15T16:54:00+00:00

My answer to How can I sell an idea to investors? on Quora

At minimum: build a prototype. If you really want then to take seriously, launch a first version and demonstrate traction.

Tags: business, entrepreneurship, startups, quora