CTOs to Know: Meet Gusto's Edward Kim

by Jess Ryan
August 19, 2016

Gusto is changing the way small companies handle payroll, benefits and HR. The San Francisco company opened a Denver office earlier this year, and they’re rapidly growing their team — including adding engineering staff in Colorado.

Gusto’s CTO and co-founder Edward Kim leads the company’s technical team and vision. Prior to starting Gusto, he was co-founder and CEO of a company called Picwing, which was acquired in 2011.

Here’s what he had to say when we caught up with him to talk tech:


What technologies power your business?

For our backend APIs we use Ruby on Rails, which serves all of our RESTful JSON API endpoints. Sitting on top of our APIs is our single-page app that is built using React.js. Other technologies we heavily rely on are MySQL, Postgres, Redis, and Sidekiq (for asynchronous jobs). We use RSpec and Mocha for testing our Ruby and Javascript code, respectively.

What upcoming tech project are you most proud of?

Some of the most interesting and ambitious tech projects we're undertaking are things that the customer will never see. For example, we've been rebuilding our backend payments system. We currently process billions of dollars in payments. All this money goes into Gusto's bank accounts from 30,000+ companies and is then routed to different employees, tax agencies and even non-profits (when employees elect to donate a part of their paycheck to charity). We need to be good stewards of our customer​s'​ funds and make sure that we can account for every single penny, and the next generation system we're building will help us to do this at the scale of $200 billion in payments.

What are the biggest technology challenges you've faced in the past? How did you overcome them?

One obstacle that we faced in the past was implementing the entirety of the American payroll tax code. In addition to federal taxes, every state has their own set of taxes, and many cities layer on their own as well. Everything is decentralized. In all, there are more than 6,000 different taxes and nearly 1,500 different tax agencies where tax payments need to be sent and forms need to be filed. They also happen to change all the time, so implementing this in a scalable way was a big technical challenge for us.

We had no problems implementing payroll taxes for our first 5 states (California, Texas, Florida, New York, and Illinois), but getting to the next 46 (Washington D.C. counts as its own "state" for payroll purposes) in a timely and scalable way proved to be daunting. We ended up writing our own high-level DSL (domain specific language) for adding states quickly. In effect, we wrote our own "state builder" language.

Here's a chart of the states we launched over time. You can really see how it accelerated over time once we built the right technologies:

What lessons have you learned about working in Colorado that other local entrepreneurs can learn from?

I've personally learned that people in Colorado are extremely friendly. In general, I've found that entrepreneurs are friendly and always willing to help a hand, but people in Colorado take this to an even high​er​ level. I think we can continue to learn from this.

How would your team describe working with you?

I'm a big proponent of feedback, so I actually have a good amount of data on this. People mostly describe me as open, authentic, a great listener, and good at giving others a strong sense of ownership.

What trends do you see happening in your industry over the next three years? How is Gusto anticipating those trends and working towards them?

I think there is a fundamental change in the way that employers are viewing the meaning of HR. Humans are not resources. They're people who, deep inside, want work on something they care about, with people they enjoy spending time with. If employers build work environments where this can happen, employees thrive and do amazing things together for the company. Whereas employers once saw HR as mainly "check-the-box," necessary evils to stay compliant with the law, they now are starting to see it as an opportunity to help build great environments at work. We at Gusto are anticipating this by building things like payroll, benefits and HR in such a way that they're not just as "tools" to stay compliant, but as "advisors" that can help guide employers and employees to make decisions to build better work environments, and subsequently a better life.

What else do you want the Colorado startup community to know about Gusto?

We're new to Colorado! Like a transplant who just moved to a new city, we're really looking to get plugged in, learn from everyone who lives here, and hopefully contribute a little bit back to the community. We have a large space right in downtown Denver, so offering it up to host events or meet ups might be the best way we can immediately give back to the community. We're also hiring our first engineering team in Denver!


Photo via Gusto. Some answers have been edited for clarity and length.


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