In 2007, when others his age were studying for midterms and living on dorm food, David Karp was busy launching Tumblr, an easy-to-use blogging platform that now hosts 17.5 million blogs and receives about 1.5 billion page views per week. The company has also attracted some $40 million in venture funding.

Karp, 24, is used to doing his own thing. At 11, he taught himself how to write code. At 15, he dropped out of high school. A year later, he got a job as CTO of UrbanBaby, a New York City parenting site. At Tumblr, Karp likes to spend his time sketching ideas in notebooks, lunching as a group with his 30 employees, and of course, perusing blogs on Tumblr. One thing he doesn't like is being pinned down. That quickly becomes clear if you try to make an appointment with him. Or happen to spot him zipping around New York City on his Vespa.

I'm very antischedule. Except for board meetings, I don't really schedule things or keep a calendar. I think appointments are caustic to creativity. It's so frustrating when you're in the middle of a great conversation or work groove, and you realize, "Oh, I've got an appointment. I've got to bolt." I prefer the "let's just call each other when we need something or want to hang out" approach. That way, I never have to cancel on people, which is always a bummer. People tell me I need an assistant, but I don't want one.

I live in Manhattan, about 15 minutes from my office. In the morning, I usually walk to work or take my Vespa. I got it in October, and I love it. I've always wanted a motorcycle, and I thought a Vespa was a good first step. It's a lot cheaper than cabs for getting around the city. It costs $5 to fill it up, and a tank of gas lasts all week.

I try hard not to check e-mails until I get to the office, which is usually between 9:30 and 10 a.m. Reading e-mails at home never feels good or productive. If something urgently needs my attention, someone will call or text me.

I used to suck at e-mail. I'd let e-mails pile up, get overwhelmed, and miss important messages-;or forget to reply. So I set up filters on my e-mail, and that's been working pretty well. Now, my inbox gets e-mails only from people in my company and from my girlfriend. A folder called Robots gets anything not written by a human, like bank statements and Google Alerts. Most everything else goes into the Unsorted folder. When I get to the office, I go through my inbox first and try to respond right away. Then I go through my Unsorted folder, but I respond to very few of those. I've found that if you're not responsive to e-mail, it trains people to leave you alone.

As I go through my e-mail, I make a list of things that I need to do that day in my notebook. I have a bad memory, so I've become a thorough note taker. I use Action Method notebooks from a company called Behance. They are really beautiful. The pages have rows of dots instead of lines. I ordered a bunch for our team. I always write with a Pilot Precise V7 pen. It's inky but doesn't smudge. In addition to to-do lists, I also use the notebooks to sketch out ideas for new features on Tumblr. The notebooks are big, so it takes me four to six months to fill one up. I keep all of the old ones in a drawer.

Every Monday morning, we have an all-team meeting in our conference room, a place I designed to be quiet and cozy. There are no conference tables-;just a couch and a few comfortable chairs. Our customer support team, a group of eight people in Virginia, attends via Skype. I started holding these meetings in January as a way for everyone to get up to speed on what everyone else is doing. The first few meetings were pretty awkward. I tend to get excited and ramble on. So I've been trying to go around the room and have everyone else talk about the projects they're working on. I still probably talk too much.

Our office is a big, open loft space, and I'm right in the middle. The engineers, who run the site, are clustered on one side of me. And the community outreach team-;the company evangelists who interact with our users-;is on the other side. People are really quiet and respectful of one another. I use headphones if I listen to music. We mostly use e-mail to communicate. I love e-mail, because it doesn't interrupt anyone. The fewer distractions, the better.

I have two screens on my desk. The first is a 30-inch Mac monitor. I always have Tumblr open in the Web browser. The second is a vertical screen, which I use only for writing code. You can turn most Dell or Hewlett-Packard monitors sideways, a trick I learned from Marco Arment, who used to be Tumblr's lead developer. I like using two screens, because if you do everything on the same monitor, you end up constantly flipping back and forth between programs, which is distracting. A lot of our engineers have the same setup now.

I'm on Tumblr all day. I don't follow a ton of people, but I post and reblog stuff I really care about. I love my blog. I get most of my news from my Tumblr dashboard. I used to be a 24-hour news consumer, but so much of the reporting is bad these days. I find tech reporting incredibly tedious and dull. And I've kind of given up on reading anything that anyone writes about Tumblr. It's often inaccurate.

I used to spend all day coding, but that changed when we hired engineers who were a lot smarter than me. I still jump in to help code as needed. The engineers have scrums every day. Occasionally, I'll sit in on their meetings to get a sense of what's going on and see if I can help with anything. I'm really good at asking questions about edge cases or unusual scenarios. So when our engineers are describing a new way to build something, I'll ask, "What if it's in a different language?" or "Will it get totally messed up if that button has to be a different dimension?" Basically, what part of this aren't we thinking about?

We roll out changes to the site every day at 11 a.m. We stagger out small changes, so we can see what works and what doesn't. We chose that time because we want engineers around if there's an issue. Plus, it's early enough that there's not much traffic. Basically, everything that was finished the day before gets pushed the next morning. It could be a bug fix or a new language file-;say, a feature that was translated into French. Or it could be a new feature that's dark launched-;the public can't see it, but we have the ability to test it.

After we launch a new feature, I keep a close eye on how many people are using it. If it's unpopular, we'll discontinue it and try something else. Every feature has some maintenance cost, and having fewer features lets us focus on the ones we care about and make sure they work very well. For every new feature we add, we take an old one out. A lot of big sites don't do that, and it's a problem. Twitter started as a beautifully simple product, but it's now going the same route as Facebook. The drive to innovate can overencumber and destroy a product. My goal is to keep Tumblr very focused.

There's kind of a hive mentality at the office. We all break for lunch between 12 and 1. Usually, one person gets up, and the rest follow. We all cram into the elevator. Once we hit the street, we break off into two or three groups and go get food to bring back to the office. Then, we all eat together.

I always carry my camera with me. In January, I bought my dream camera, a Leica M9. It's the smallest digital camera they make with a full sensor. I post lots of photos on my blog, and I actually took most of the Tumblr employee photos.

I don't do much of the hiring anymore. Each department is in charge of hiring its own members. I like autonomous people. I want people who can take a project and figure out how to do it themselves. I don't really care about how things get done. Only that they get done.

Lately, I've been focused on our community outreach team-;it's responsible for figuring out how to connect with and promote the people who use Tumblr. I recently brought in my friend Richard Tong to be our fashion editor. He started Weardrobe, a fashion website that is now owned by Google. About 18 percent of our blogs are fashion related, and he focuses on reaching out to that demographic. As a result, Tumblr had a huge presence at New York's Fashion Week. I meet with the community team at least once a week to brainstorm about ways we can connect with users, like sponsoring a literary event or organizing meetups for Tumblr users around the world. I love that part of my job.

Usually around 3 p.m., I need a pick-me-up. A handful of us will pop out for tea at a place around the corner. I either order an iced tea or an Armenian mint tea. I used to drink coffee, but it messes me up-;I have a very fast metabolism, so I go from drowsy to unbearably hyper. Tea has just the right amount of caffeine.

In the afternoons, I usually want to bury my head in some project-;either screwing around with design or coding something. Recently, I took a stab at redesigning our photo sets feature, which lets users post several photos together, like a slide show. I may spend a couple of hours scraping together my thoughts before sending an idea out to the product team to get their take on it.

One or two nights a week, I usually work late-;until 8 or 9. When I do, I like to see who is still in the office and then take them out for dinner as a way to say thank you. We are surrounded by great restaurants, so we go somewhere nice.

I rarely work on weekends unless there's a serious database or infrastructure emergency. The company is growing fast, and we've had some problems scaling. Any time we add capacity, it immediately fills up. In December, the site was down for an entire day. It happened on a Sunday-;there was a whole lot of scrambling to figure out what broke. Everything about it sucked.

One of my favorite things to do on the weekend is take road trips. I just joined the Classic Car Club in Manhattan. You pay an annual fee, which gives you access to all these cool cars. My girlfriend and I took a 1996 Porsche 993 Carrera 4S up to Montreal one weekend. It was amazing. We've also taken trips to Boston and Maine. Other times, we'll jump on the Vespa and drive around the city. We might have brunch at our favorite place in the East Village, then pop over to see friends in Brooklyn before heading back up to Union Square to see a movie.

I spend a lot of time with people who work at Tumblr, but I make a very poor effort to hang out with other people in my life. I'm trying to do a better job of that. But, honestly, I love quiet nights at home. My girlfriend is a spectacular chef. She usually cooks dinner for us two or three nights out of the week. And then we wind down by watching TV. We use Apple TV to watch television shows from iTunes. We both love Futurama. I recently got her into Top Gear, a car show on the BBC.

Sleep is precious to me. I'm very disappointed if I don't go to bed before midnight. We have a rule: no laptops in the bedroom. Being on computers all the time makes me feel gross.

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