There’s a pre-conceived notion that it’s difficult to build a large business in a well defined segment with an established player. The best entrepreneurs don’t see it this way. They care about unmet user needs and how they can solve them. A crowded market is simply validation that the problem exists.

I love companies going after an established market because they represent what the future of software will be like: building is easy, distribution is hard. Cal.com is one of these products — they’re going after the scheduling market.

I’ve followed them for a while and managed to chat with their founder. Read on to see why I’m excited about the product, and the founder’s vision for the company.

I started following Cal.com due to the following:

Calendly, the incumbent in the space, started in 2013. They were last valued at $3 billion. They raised $350 million in their last funding round.

Building in this market for a specific niche (e.g. booking software for hairdressers) seems reasonable. Building a lifestyle business that solves an acute pain point very well seems reasonable. But if you said you were building general purpose time management software, people will call you crazy.

Cal.com chose crazy, and I love them for this. I figured they’d have a unique way of looking at the problem space. Cal.com wants to become the infrastructure for time. They want to build an ecosystem of applications that help you manage time.

Between June 2021 and October 2022, they acquired 2,400 monthly active users. During the same time, they’ve got nearly 14K Github stars (one of the best measures of traction for open source projects).

Open source is a common GTM model for dev tools and data products. Running an open startup is a different ball game. Everything is public: salaries, the number of customers, funding etc.

Transparency encourages independence. People have all the information they need to do well in their job. It comes with its fair share of challenges though. Cal.com clearly believes the benefits outweigh the downsides.

I asked Peer, the co-founder and co-CEO of Cal.com, if he’d be happy to answer a few questions and he kindly agreed. Here’s what he had to say:

Why did you decide to go after the scheduling market?

I was working on leanhire.com, a marketplace for contractors to become full-time employees and was looking for an open scheduling tool that I could self-host and change code.

Why did you decide to build Cal.com in the open?

It just felt like the natural next step after open-sourcing the codebase. I never liked the intransparency around salaries and we quickly realised that we can tap into incredible talent markets by having a global salary, vs localised salaries.

What is your best advice for people considering starting something in an area where a large incumbent dominates?

Have a big enough differentiator. For us, SaaS vs Open-Source is fundamentally different. It’s probably not enough to launch a “Calendly, but with nicer buttons”. That’s not gonna work.

While we share a lot of product overlap with Calendly, our target customer is fundamentally different: customers who need something highly customisable, embeddable and self-hostable that fits their compliance needs.

In the early days, how did you convince your early users to use your product instead of Calendly.com?

Honestly, no idea. We had a ton of traction before we wrote the first line of production code. I started this project as calendso.com without any commercial interest, I just needed something for myself and outlined the features I would need/build on a landing page with a waitlist.

We then piped every signup into Slack.com and started going. I believe Hackernews was the first “viral” effect and then the amazing Product Hunt launch (Product of the Month) really pushed the product forward.

Did you always want to go down the open source route? What was the thinking behind this?

Yea. It was a hard requirement for what scheduling solution I wanted to integrate at leanhire.com.

What are some of the things to be aware of when you operate a company as open as Cal.com?

Be very mindful around the privacy of team members and user data. You can’t publish everything for obvious reasons. All public salaries are opt-in, however, no team member has yet refused to publish their salary and they really love it – counterintuively to most advice out there.

Anything else that comes to mind?

Timezone math is hard. Do not recommend.

Innovation never stops. If there’s a large player or several large players in a market, it doesn’t mean you can’t go after it.

Start by figuring out who you want to serve and for what need. It’s important to answer this question before getting into the details. Otherwise, you end up in a feature battle (i.e. I have this feature but Y don’t have it).

Balance your short-term goals with a long-term vision. As the builder, you need both. Your customers only care about the problem you are solving for them. But for you, as the builder, it’s important to think about the long-term vision. This drives several decisions: how much money you need, the kind of team you want to build and what you prioritise in terms of features.

Here’s to more stories like Cal.com.