As a value proposition, the word "design" suggests aesthetics, functionality, and thoughtful consideration of the target audience. Smart companies apply design thinking to products and to customer experiences, but rarely to internal processes. Main Street Hub is an exception.

Main Street Hub is that rare creature--a startup more in love with its customers than with its technology. Typically, it is entrepreneurs who are lauded as the "backbone of the global economy." But co-CEOs Andrew Allison and Matt Stuart use those words to describe the small, local merchants who are the market for their social-media management services. "These people are so important, and no one works harder than they do," says Allison. "We have a reverence for them."

Allison and Stuart discovered the distinctive challenges of mom-and-pop-dom while trying and failing to start an online guide for consumers seeking mechanics. The auto-repair shop folks--as well as owners of pizza parlors, beauty salons, independent gyms, and their ilk--understand that, for businesses of all sizes, online marketing is table stakes. But "the auto mechanic doesn't put down the wrench, get out from underneath the car, and go send Tweets," says Stuart. "He doesn't have time. He doesn't have the interest. And he doesn't have the resources."

Local businesses, the founders observed, don't want to manage social media. Nor do they want to manage tools that help them manage social media. What they do want is someone to unsling that particular albatross from around their necks. So Allison and Stuart created what is, in essence, an outsourced social-media department, customized for each merchant. Reduced the price of buffalo wings at happy hour? Got a mash note from a happy customer? Been reviewed by someone who urges Yelp to introduce a negative-star option? Main Street Hub steps in to promote, amplify, or mollify, as circumstances warrant. More than 5,000 small companies use the service, which costs between $249 and $399 a month for most industries.

Allison and Stuart learned about design thinking at Stanford, where they met. (Main Street Hub, which launched in 2010, is based in earthier, edgier Austin.) Process creation in companies generally involves little more than blocking and tackling. Design thinking, by contrast, mandates empathy for the user and an understanding of his or her context, as well as the deployment of constant small experiments. That's how the founders of Main Street Hub developed all their processes, from sales and customer service to human resources. "What we do with our customers we also do internally," says Allison. "The process side of design doesn't get much attention, but it is really interesting."

Main Street Hub's design approach began with sales, which the founders handled personally for the first six months in order to conduct tests. "We came in with no preconceived ideas about how to bring customers onboard and started by talking to people, then prototyping and testing," says Stuart. "We tested should we show or tell? Is it easier for the merchant to talk in person or over the phone? Do we use this or that type of demo? It was very iterative." Typical of the observational fieldwork that is a hallmark of design thinking, "we worked right next to our customers, understanding what was going to be the best method of educating merchants about our product," Stuart says. (He describes the process they ultimately arrived at as "consultative.") On the service side, the company tested, among other things, the optimal number of managers to assign to each customer, whether or not to use dedicated managers, and the optimal frequency for customer check-ins.

Design thinkers get as close as possible to the thing itself, so the company developed a hiring process that requires candidates to complete an assignment simulating some aspect of the job for which they are applying. It has iterated that process as well, shifting the simulation farther and farther back to maximize opportunities for feedback. Now the company does it "even before diving into the meat of the interview process," says Stuart. Main Street Hub has also experimented with its paid time-off policy, moving from one with a set number of sick and vacation days to one where employees are free to use their days however they like.

Another design-thinking principle--dubbed "composting" by Michael Dearing, who teaches the Launchpad entrepreneurship class at Stanford's keeping the memory of failures alive to provide future insights. Allison gives the example of Main Street Hub's feedback mechanism, which started life as a shoebox with a slot cut into the lid and evolved into an online tool--both versions anonymous. "Then it occurred to us that the anonymous feedback channel ran a bit contrary to the transparent culture that we were building. So we scrapped it, leading more to a culture of face-to-face conversations," says Allison. "But we keep that experience close and frequently cite it as we think of other initiatives to capture feedback and enhance communication."

With design thinking bred in the company's bones, Allison and Stuart say they will apply it to every product and every process, even as they scale. Main Street Hub is doubling in size annually: This year, it was No. 72 on the Inc. 500, with 2013 revenues of $9.2 million. That kind of rapid growth requires changes based on a deep, observed understanding of how customers and employees think and behave. "We will never stop prototyping or iterating," says Allison. "We don't want to wait until something outgrows its usefulness or breaks down."