Improbable: enabling the development of large-scale simulated worlds

Over the past decade, computing resources that were previously available only to large organizations became available to almost anyone. Using cloud-scale development platforms like Amazon Web Services, developers can write software that runs on hundreds or even thousands of servers, and do so relatively cheaply.

But it is still difficult to write software that makes efficient use of this abundant computing. For some projects, like creating websites, there are well-known software architectures that work reasonably well. In other areas, there’s been progress building generalized tools (for example, Hadoop in data processing). For the most part, however, developers need to solve the parallelization problem over and over again for each application they develop. New tools that help them do this are sorely needed.

Today, I am excited to announce that a16z is investing $20M in Improbable, a London-based company that was founded by a group of computer scientists from the University of Cambridge. Improbable’s technology solves the parallelization problem for an important class of problems: anything that can be defined as a set of entities that interact in space. This basically means any problem where you want to build a simulated world. Developers who use Improbable can write code as if it will run on only one machine (using whatever simulation software they prefer, including popular gaming/physics engines like Unity and Unreal), without having to think about parallelization. Improbable automatically distributes their code across hundreds or even thousands of machines, which then work together to create a seamlessly integrated, simulated world.

The Improbable team had to solve multiple hard problems to make this work. Think of their tech as a “spatial operating system”: for every object in the world — a person, a car, a microbe —the system assigns “ownership” of different parts of that entity to various worker programs. As entities move around (according to whatever controls them  — code, humans, real-world sensors) they interact with other entities. Often these interactions happen across machines, so Improbable needs to handle inter-machine messaging. Sometimes entities need to be reassigned to new hardware to load balance. When hardware fails or network conditions degrade, Improbable automatically reassigns the workload and adjusts the network flow. Getting the system to work at scale under real-world conditions is a very hard problem that took the Improbable team years of R&D.

One initial application for the Improbable technology is in gaming. Game developers have been trying to build virtual worlds for decades, but until now those worlds have been relatively small, usually running on only a handful of servers and relying on hacks to create the illusion of scale. With Improbable, developers can now create games with millions of persistent, complex, interacting entities. In addition, they can spend their time inventing game features instead of building back-end systems.

Beyond gaming, Improbable is useful in any field that models complex systems — biology, economics, defense, urban planning, transportation, disease prevention, etc. Think of simulations as the flip side to “big data.” Data science is useful when you already have large data sets. Simulations are useful when you know how parts of the system work and want to generate data about the system as a whole. Simulations are especially well suited for asking hypothetical questions: what would happen to the world if we changed X and Y? How could we change X and Y to get the outcome we want?

Improbable was started three years ago at Cambridge by Herman Narula and Rob Whitehead. They have since built an outstanding team of engineers and computer scientists from companies like Google and top UK computer science programs. They’ve done all of this on a small seed financing, supplemented by customer revenue and research grants. We are thrilled to partner with Improbable on their mission to develop and popularize simulated worlds.

Stack Exchange

Today we are announcing that A16Z is leading a $40M investment in Stack Exchange, along with earlier investors USV, Bezos Expeditions, Spark, and Index.

Stack Exchange is a network of 133 sites (and growing) where people can ask and answer questions about topics related to engineering, science, hobbies, and more. The biggest site on the network is Stack Overflow, which alone gets over 40 million unique visitors per month. The other sites cover a very wide variety of topics, including: math, gardening, English language usage, graphic design, physics, cryptography, chess, astronomy, Buddhism, data science, martial arts, home improvement, photography, bicycles, board games, economics, to name a few. Most likely, you’ve used Stack Exchange without even knowing it —the network had over 300M unique visitors last year. Many users come in through Google, get their answer, and then leave, usually a little bit smarter.

One of the major startup opportunities of the information age is: now that more than two billion people have internet-connected devices, how do we create systems to efficiently share and store their collective knowledge? Requirements for successful collective knowledge systems include: 1) users need to be given the proper incentives to contribute, 2) the contributions of helpful users need to make the system smarter (not just bigger), and 3) users with malicious intent can’t be allowed to hurt the system.

Many entrepreneurs and inventors have tried and failed to solve this problem. As far as I know, only two organizations have succeeded at scale: Stack Exchange and Wikipedia. Stack isn’t as large as Wikipedia on the readership side — the topics are more specialized—but, on the contributor side, is closely comparable to Wikipedia. Last year, Stack had over 300 million unique visitors, and 3.8 million total registered users, who contributed over 3.1M questions, 4.5M answers, 2.7M edits, and 17M comments.

Stack’s business model is based on job placement. Employers create company pages (here is Amazon’s—over 6000 companies have created pages) and then run targeted ad campaigns for open job opportunities. Revenue has grown quickly, and the company employs over 200 people. The HQ is in NYC, with offices in Denver and London, and remote workers in Israel, Brazil, Japan, Germany, Slovenia, France, and across the US.

I believe Stack Exchange’s growth has now reached escape velocity. Not only will the existing topics continue to grow, but many new topics will emerge, until the network covers every topic that is amenable to objective Q&A. As new generations of people grow up on the internet, old habits — searching through textbooks or how-to books, or asking friends—will fade away. People will come to expect that any objective question can be instantly answered with a Google search.

I’ve been a personal investor in Stack since its initial funding, and it has always been one of my favorite investments. Stack’s cofounder & CEO, Joel Spolsky, is an amazing entrepreneur and internet visionary. I’m very happy to back him again with this new investment.


I’m excited to announce today that Andreessen Horowitz is leading a $3M financing of Skydio, a startup developing artificial intelligence systems for drones.

The Skydio team is awesomely qualified. They worked on drone vision systems at MIT and then co-founded a drone project at Google[x] called Project Wing. The company’s mission is to create smart drones. As cofounder Adam Bry says:

Drones are poised to have a transformative impact on how we see our world. They’ll enable us to film the best moments of our lives with professional quality cinematography and they’ll also change the way businesses think about monitoring their operations and infrastructure. This grand vision is starting to come into focus, but existing products are blind to the world around them. As a consequence, drones must fly high above the nearest structures or receive the constant attention of an expert operator. “Flyaways” and crashes abound. These problems must be solved for the industry to move forward.

Smart drone operators will simply give high-level instructions like “map these fields” or “film me while I’m skiing” and the drone will carry out the mission. Safety and privacy regulations will be baked into the operating system and will always be the top priority.

This is my second drone investment – the first one was Airware. I see Airware and Skydio as complementary (and I’d like to make more drone investments – at any stage including seed investments – as long as they don’t compete with Airware or Skydio). You can think of Airware as the operating system and Skydio as the most important app on top of the operating system. The founders of both companies have deep expertise in both aviation and computer science, the key prerequisites for creating smart drones.

Here’s a fun video of an early Skydio prototype in action: 


I was chatting with John Borthwick a few years ago and he said something that struck me. He said he was interested in companies that appear to be focused on selling X but are really online communities that happen to make money selling X. This helps explain why many investors are confused by the sustained success of these companies. One example he cited was GoPro. Many investors decided not to invest in GoPro because they saw it as a camera company, and camera companies generally get quickly commoditized. However, investors who properly understood GoPro saw it primarily as a highly engaged community of sports enthusiasts, something that is very hard for competitors to replicate.

Shortly after that conversation I got an email from Jordan Cooper about a company he was investing in called Soylent that was taking an open-sourced approach to developing science-based food products. “The community and engagement around the product is pretty amazing to me – there’s something interesting happening here,” he said. He was referring to Soylent’s very active discussion forum, as well as the DIY Soylent site where users share their own Soylent recipes. Seen through the lens of Borthwick’s comment, it was an obvious investment – a few days later we signed a term sheet to lead the seed round.

Soylent is a community of people who are enthusiastic about using science to improve food and nutrition. The company makes money selling one version of that improved food (some users buy “official Soylent,” others buy ingredients to make their own DIY Soylent recipe). If you look at Soylent as just a food company, you misjudge the core of the company, the same way you would if you looked at GoPro as just a camera company.

Why are Soylent users enthusiastic about applying scientific methods to develop food? You might wonder why the nutrition advice you hear seems to frequently change. When I was growing up, we were told to reduce our saturated fat and increase our carbohydrates. Now we are told the opposite. As Vox explains in this excellent article, that’s because food science has been distorted by the influence of food companies:

Many of the health policies and personal dietary choices we made related to fat (and saturated fat in particular) were based on very flawed and biased evidence. Contradictory research findings that challenged the paradigm were systematically stifled and ignored, and self-interested researchers — as much as Big Food — shaped the research agenda, media reporting on diet, and public perception.

There was very little incentive in the past to invest in the science of food and nutrition. Traditional food companies are primarily marketing and distribution companies. They blanket the earth with advertising and fight to distribute their products as widely as possible (while blocking the distribution of competing products). As a result, it is very hard to get food that is convenient, affordable, and nutritious outside of wealthy areas where organic and other premium food is available. If you read the Soylent forums you’ll see that – contrary to the caricature of Soylent as a complete food replacement – it mostly replaces unhealthy meals:

“I do it because the alternative for me is to swing by a gas station for a Krispy Kreme donut or three, or stop by a fast food restaurant and pickup a few things off the dollar menu for lunch.” source

“Personally, I don’t really care for cooking. I usually feel that a meal should take longer to eat than to cook. That leads to meals that are more “assembled” or “heated” than actually cooked, just sandwiches, hotpockets, and anything microwaveable. This is not a healthy diet. So Soylent seems like the right fit for a healthy diet with very little food prep effort.” source

“During a typical week there’s several meals I eat alone in front of the TV, weekday dinners mostly. Those were usually fast food, or frozen or canned. So I thought Soylent would be faster, easier, and healthier than what I had been doing before. I still eat out with friends several times a week, and the food at work is actually quite good.” source

Soylent inverts the Big Food business model, spending nothing on advertising and distributing solely through e-commerce. Soylent’s “marketing plan” is to invest in its online community and in peer-reviewed scientific studies. The belief is that the internet has made people smarter, and that the old tactics of selling junk food using clever advertising will be increasingly ineffective. We have all sorts of food-related problems in the world – malnutrition, diabetes, and obesity, to name a few. Part of the solution to these problems is providing people with better scientific research, and more food choices that are convenient, nutritious, and affordable.

Today we are announcing that Andreessen Horowitz is leading a $20M investment in Soylent, alongside our friends at Lerer Ventures and Index Ventures. Since the seed round in 2013, Soylent has grown quickly and now generates millions of dollars per month in subscription revenues. The company is profitable and doesn’t need additional capital (our favorite kind of investment), but decided to take money to invest in long-term R&D. In addition to improving the current product and introducing new products, the focus will be on dramatically reducing the price of Soylent, from the current $3 per meal to a fraction of that. We are very excited to continue working with Rob and his team on this important project.


Today, I’m excited to announce that Andreessen Horowitz is investing $50 million in BuzzFeed. As part of the investment, I’ll be joining the company’s board.

Many of today’s great media companies were built on top of emerging technologies. Examples include Time Inc. which was built on color printing, CBS which was built on radio, and Viacom which was built on cable TV. We’re presently in the midst of a major technological shift in which, increasingly, news and entertainment are being distributed on social networks and consumed on mobile devices. We believe BuzzFeed will emerge from this period as a preeminent media company.

BuzzFeed started out focusing on lightweight content like memes, lists, funny photos, etc. This led some industry observers to dismiss Buzzfeed as a “toy”. The company has since moved steadily up market, following the typical path of disruptive technologies. It now has an editorial staff of over 200 people covering a wide range of topics – politics, sports, business, entertainment, travel, etc – and plans to invest significantly more in high-quality content in the coming years.

We see BuzzFeed as a prime example of what we call a “full stack startup”. BuzzFeed is a media company in the same sense that Tesla is a car company, Uber is a taxi company, or Netflix is a streaming movie company. We believe we’re in the “deployment” phase of the internet. The foundation has been laid. Tech is now spreading through every industry and every part of the world. The most interesting tech companies aren’t trying to sell software to other companies. They are trying to reshape industries from top to bottom.

BuzzFeed has technology at its core. Its 100+ person tech team has created world-class systems for analytics, advertising, and content management. Engineers are 1st class citizens. Everything is built for mobile devices from the outset. Internet native formats like lists, tweets, pins, animated GIFs, etc. are treated as equals to older formats like photos, videos, and long form essays. BuzzFeed takes the internet and computer science seriously.

As a small, early investor in BuzzFeed, I got to observe firsthand how effectively Jonah and the team executed in recent years. The results speak for themselves: BuzzFeed now reaches over 150M people per month, is consistently profitable, and will generate triple digit millions in revenues this year. I believe the future of BuzzFeed – and the media industry more generally – will only get brighter as the number of people with internet-connected smartphones grows, and the internet solidifies its place as the central communication medium of our time.