Successful, customer-driven companies put their customers first in everything they do. Even if those customers have four paws.

BARK, the company behind the wildly successful BarkBox, was created when its founders wanted to make functional and stylish products that would make their dogs happy. As co-founder Henrik Werdelin says, BARK does everything from a dogs-eye view.

Personalization has been a hallmark of the company, especially with its monthly subscription boxes that have served more than 3 million dogs. But instead of viewing the company as a subscription box company, Werdelin says BARK views itself as a company in the business of making dogs happy, which is best done through subscription boxes.

Each monthly BarkBox comes with two treats, two toys and a chew for the dog. But Werdelin says the reason it’s so successful is because of the experience it provides for owners to share something special with their dogs every month. The products are exclusive to BARK and fit a monthly theme for the box.

Taking things to the next level is BARK’s amazing attention to personalization. Of the one million boxes it sends out each month, there are around 120,000 different varieties based on the size and breed of the dog and things like allergies. Personalization also comes in the form of tailoring boxes to individual dog’s needs. The BARK team makes an effort to talk to as many customers as possible, which usually ends up being around one-third of its customers each month. From those interactions, the company’s Happy Team, which focuses on customer experience, created the No Dog Left Behind program. If a customer calls in with a certain request for a product, the team goes out of its way to make it happen. At one point the team had 20,000 boxes going out, each one hand assembled with notes of the customer’s request. One customer didn’t want pork treats in the BarkBox for her pig, so the team handmade her a box with treats for pigs. Other customers called wanting toys that could withstand their aggressive chewer dogs, so BARK made a new line of products and put them in those customers’ individual boxes.

The company has since built technology to match the needs of the team and customers and to scale the personalization process. But Werdelin says his best advice is to do things that don’t scale. Companies often want to create big systems to solve problems by mass, but customers are unique. The best solutions happen when a company and its employees have empathy and think of what’s best for each individual customer. Most brands can do something manually for a long time before coming up with a scalable solution. BARK even sends out and answers its customer emails individually to gain insight and build strong customer relationships.

Personalization is the root of BarkBox’s success. Paying attention to individual needs and really taking the time to not only listen to customers but go above and beyond to meet their needs makes a difference. By putting customers and their dogs first and making their lives easier and better, BARK has secured loyal customers—both humans and canines.