As the founder and CEO of Applico, the platform innovation company, I feature stories in this column, Tipping the Scale, from platform founders on how they hit critical mass. This week I spoke to Joel Spolsky, CEO of Stack Overflow, a question-and-answer content platform for software developers, by software developers. We spoke about the origins of his company, how he solved the chicken-and-egg problem, and how Stack always manages to be the number 1 search result when a developer looks up a programming question on Google.

The following are seven platform takeaways from our discussion.

1. Understand platform innovation: Don't put up paywalls on content platforms with large amounts of user-generated content

Stack Overflow was able to disrupt Experts Exchange, a similar programmer Q&A community that charged programmers to access answers. It was the dominant platform at the time and had been founded 12 years earlier.

As Joel explains, "Experts Exchange was a pay website that had hacked Google in some weird way. It looked like they had the answers to all the questions. To read the answers, you had to pay, and this was endlessly annoying to programmers. That was our first mission, to make that user-generated content (programmers helping programmers) public."

A lot of the people that Experts Exchange was blocking out with its paywall could've also been producing value to the rest of the community. Stack Overflow's successful overtake suggests implementing a paywall on a content platform that can derive a great deal of its content from its own consumers will severely limit the platform's potential.

2. Solve the chicken-and-egg problem: Rig one side of the equation

Uber needed to solve for whether it got drivers or riders on the platform first. Stack Overflow had a similar dilemma; it needed valuable content in place if it expected programmers to return to the community. This is the chicken-and-egg problem.

Luckily for Stack Overflow and its developer community, Joel had built a community and a following of 30,000 developers with his wildly popular blog, Joel on Software. In 2008, Joel announced Stack Overflow on his blog and immediately "30,000 people visited the site and that was the seed of the content," he says. Along with this traffic, Stack Oveflow attracted its earliest content producers.

Fun fact: When you count the most active users, the ones who do at least five things a month, Stack Overflow has more than 30,000--as many as the English version of Wikipedia.

3. Fail quickly

Joel highlighted the importance of making experimentation part of business as usual. "Over the years, my first company, Fog Creek, tried a lot of things," he says. "Some were successful and others weren't. On average, we tried one new business per year. The most successful experiments, Trello and Stack Overflow, became their own spinoff companies with their own CEOs and investors. Some of the more unsuccessful experiments included a curriculum to teach developers how to make better software and a job board for programmers in India. We ended up selling one job posting for something like 25 rupees. We closed it immediately."

In January of this year, Stack Exchange, operator of Stack Overflow, raised $40 million led by A16Z at a valuation of more than $400 million. The experimenting paid off.

4. Stick to your true north: Focus on the most passionate segment of your user group, especially if they are your prosumers

Prosumer = producer + consumer

Etsy has a lot of prosumers. Its consumers purchasing artisanal goods are also selling artisanal products (producing platform value). This is user group overlap.

Stack Overflow is unapologetic about its commitment to developers. "We're here to serve the developer community," says Joel. "If any activity doesn't help developers or people who act similar to developers, we're not interested. We're able to maintain a high level of quality content because we focus on our core constituency."

Like Etsy, Stack Overflow's focus on this passionate user segment enabled it to have users acting as both producers and consumers.

This commitment was a major driving force to create Stack Overflow Careers, a complementary service marketplace that helps developers and employers find one another.

5. Set rules and standards: Reward your hardest workers

A content platform, like a magazine, depends on strong content and eyeballs. However, a content platform doesn't have to create any content. Stack Overflow sits in the middle and enables content producers to connect with consumers of their content.

A major component of this delicate triangular relationship between platform, consumers, and producers is to create incentives for producers to continue creating quality content.

Joel explains, "We always knew we wanted developers to answer questions. If they found an answer they liked, they could upvote that answer. We always knew the behaviors we wanted to promote on our system. There is a reputation number next to user profiles, and it's the best approximation of a user's contribution. The reputation causes people to behave in an exemplary way. We also have badges that users can earn." The more badges and reputation points that a user has, the more privileges the person is able to exercise on the platform (creating new tags, deleting comments, etc.).

I found it very interesting that Joel and his team use their content's position in search results as a KPI for content quality.

In fact, Stack will shut down an entire Q&A site (there are 150) if the company thinks the content from that site is worse than everything else on the same topic on the internet. "Why do this is if our content is number 9 on a page? We want to be the best content available to developers," says Joel.

6. Incentivize good behavior: Externalize innovation and management

A major benefit and cost saving of the platform business model is the concept of externalized management. What do we mean? Let's take Uber as an example again. Uber drivers don't need managers. They clock in through the app, the app guides them to customers, and they clock out. An efficient platform doesn't require much managerial oversight to operate.

For Stack Overflow, users police the site. They identify and promote rock star content and hide content that is subpar. A majority of this work is completed by Stack's user base.

Furthermore, Joel explained, Meta Stack Overflow puts users to work for the platform's benefit. Users can post bugs, complaints, and suggestions for Stack Overflow on Meta. This is a perfect example of a platform leveraging its user base to externalize innovation and management.

7. Narrow your focus: Critical mass can be achieved with less than a thousand people

The lifeblood of a social content platform is quality content.

Everyone talks about achieving critical mass as a multiyear journey and endeavor. This is true to a certain extent; however, if you narrow your network effects to a smaller, more well-defined community, you can achieve critical mass with a smaller quantity of users.

It's for this reason that Stack Overflow is very cautious as to when it allows a new topical channel to go public. "We've created 150 sites on the Stack Exchange network on different topics, and we don't allow them to open without a critical mass of people willing to contribute," says Joel. "This prevents a person from asking a question on a site and not getting an answer. We define critical mass as 200 very active people and 500 to 1,000 not so active people."

Furthermore, Stack Exchange has an experimentation zone called Area 51, where users can propose new channels. If they receive enough signups, Stack Overflow then allows sites to move forward.

Think in smaller milestones to make your long-term goals a reality.