Founder's Guide
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Founder’s Guide to the Y Combinator Interview

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Twice a year, I get a ton of cold emails asking some version of the following question: how can I do well in my Y Combinator interview?

Rather than try (and fail) to respond individually, I put together the following best practices document, based on my experiences as a YC alumnus and former partner.


YC has evolved – a lot

Thirteen years ago, I walked into my Y Combinator interview with founders Paul Graham, Jessica Livingston, Trevor Blackwell and Robert Morris.

A lot has changed since then. Back in 2005, when I interviewed during the first-ever YC batch, it was very technology-focused. There wasn’t as much of a focus on business or monetization. Our 40-minute interview for our AJAX calendar website Kiko was primarily spent debating with Trevor Blackwell and Robert Morris on whether client-heavy javascript apps would become mainstream or not (turns out we were right in the end ;)).

Fast forward to 2018 and YC is a well-oiled machine. Over 1,900 companies have gone through YC, giving the partner team a generous sample size to identify positive and negative traits in early-stage companies. You can’t get accepted into YC solely on the premise of your idea; you need to convince the partners that you are amazing founders who can build a large business.

There are a lot of technically-focused guides on YC interviews, like Yuri’s at Hackernoon that I highly recommend. As a 3-time alum, former partner, and someone with close ties to the YC community today, I’ve seen the best and worst and wanted to share my own perspective.


Get these 3 things right

Later on, I’ll share some prep tips and more specific interview advice. But first I want to convey the three factors that will make or break your interview. If you take anything away from this article, it should be these three things!

1. Know what you’re doing

The most important outcome of your YC interview is to convince the interviewers that you are a great founding team. How do we judge that? Through a short, 10 minute interview, we make a judgement on the founders primarily on the confidence they project, and their expertise in their industry. You can demonstrate this in two ways.

Know your business inside and out

You don’t need to know all the answers to every question, but you want to show that you’ve explored every pathway in the maze of your space. Balaji Srinivasan’s concept of “the idea maze” describes what you want to convey.

When I was a partner, I’d often fire off questions like “have you tried [growth channel]” or “what about building [feature].” There’s only so much you could have done to that point, so the answer didn’t always have to be “Yes, we’ve already tried that.” But it was important that you had considered every area of your business, and had a plan.

If I’m asking about a growth channel or feature, it is ok for the answer to be “yes, we are going to do it”, “no, we won’t do it”, or “we need more data to make a decision”: the important part is that you have a roadmap that prioritizes what you are going to do, and you have well thought out reasons for how you created that roadmap.

If I’m looking at your idea with fresh eyes and identifying angles that you haven’t thought of, that is generally not a good sign. Investors want to know you have a comprehensive, rigorous plan.

Know your core metrics

When I interviewed founders and they didn’t know their core metrics, it was a huge red flag. The core metrics can be whatever you think is important (often I would ask founders which metrics were important) — but whatever you’ve selected, you should know them (and how they are changing daily, weekly or monthly) off the top of your head.

Once you identify the metric that’s important, you need to show that you know all the information around it. For example, if you say that DAU is your north star metric, don’t stop there:

  • What is your DAU as of today?
  • How fast are you growing week-over-week? Month-over-month?
  • What actions are you taking to grow it? Homepage testing, funnel optimization, doubling down on a marketing channel?

Being able to drill down into your metrics serves two functions:

  • Presents a positive business case for investment (assuming the numbers are favorable).
  • Demonstrates that you are a data-driven founder who will build a company that stays focused on the numbers that matter — and constantly works to improve them.

When you don’t have metrics, it’s an early indicator that you won’t create an iterative feedback loop that will improve your startup systematically over time.

2. Understand the small and big idea

As Andrew Chen accurately describes, startups have two major growth stages:

  • Zero-to-one
  • One-to-n

Mastering each one requires an understanding of what I call the small and big idea.

Small idea

To get off the ground, you want to show that you understand how to dominate your core niche – a la Kevin Kelly’s 1000 True Fans concept.

A narrative that describes how you encountered the problem, built it for yourself, then talked to 100 other people like you is tried and true for a reason: it shows that you are an expert in this problem space, you’ve done your homework and are now building a product with feedback from real customers.

You should be able to convey the reasons why you’re going to attack — and dominate — a niche area with your product.

Big idea

But we all know that the end goal isn’t to own a very small niche, but to use that as a platform to successfully enter a much bigger arena. You’ll get asked about this, and better yet, you can actively guide the conversation in that direction.

What is the biggest idea you can convey on how this niche product grows into something huge? Expansion can happen in many ways, often by expanding geography, product category, or target customer. The important part is that you make a bold claim (that you believe) about how you will grow into something much bigger once you dominate your core niche.

3. Convey Founder Synergy

While a handful of unicorns and other rocket ships have famously overcome founder rifts, more often than not, it will derail a startup.

Your interview should be a demonstration of the great synergy on the founding team, and you don’t want to undermine that in any way. It may sound obvious, but I’ve seen founders talk over each other or disagree during their YC interview! When you’re a YC partner considering hundreds of potential entrants, visible founder infighting is all you need to say “next”.

Beyond your in-person demeanor, you also want on-paper synergy.

Partners look for a team that’s balanced. Having founders with complementary skill sets or areas of focus can be important. It’s completely fine if all founders come from a technical background, but one should be able to say “I’m focusing on operations” or “I’ll be in charge of marketing.”

If the founding team has worked together or has history, it’s also a good point to bring up. Not a necessity, but helps show that you have worked together and there’s one less unknown variable to worry about with your company.


How to prepare

Those are the most important aspects of your interview, but there’s much more you can do to set yourself up for success. Great YC interviews start weeks before you actually walk into the room to speak with partners.

It’s simple, and no one wants to hear it, but it helps to practice — a lot. Expose yourself to people who have been through interviews before, as this will reduce the chances that you’re thrown off by a stray question.

1. Find people who have done it

The YC ecosystem is big enough that there’s no excuse for failing to get help. A couple starting points:

  • YC network: Look through the list of all YC companies and identify anyone you know or could get an intro to.
  • Startup School: Go to the events or reach out to alums who offer to give free interviews.
  • Your own network: If you’re in any way involved in the startup community, post something to Facebook or LinkedIn. All it takes is one friend of a friend to get you started.

2. Talk to them

After you’ve connected with people who can help, ask them to interview you — or at the very least, send you questions. You’ll be surprised by the different types of questions that you otherwise wouldn’t have considered. That’s the point!

Better to be taken aback in practice than in the real game.

3. Write your answers down

Write down all your answers as concisely as possible and rehearse, rehearse, rehearse.

You don’t want to think on the fly. When you write down and repeatedly review your answers, they’ll be drilled into your head so deeply that you don’t have to worry about saying the wrong thing.

4. Practice the interview under extreme circumstances

A friend of mine whose wife recently got accepted into YC shared a hilarious but clever tip: practice under manufactured duress. He told me that he would literally throw socks at her, dance in the background, or yell at her while she was reviewing answers — anything to try and throw off her focus.

This is how you mimic the intensity of getting grilled by YC partners, some of whom you may have looked up to for years.

Once you’ve prepared for the worst, the interview will feel tame by comparison.


Specific interview tips

You know the big picture and have practiced your answers – now it’s time for the real thing. Keep these guidelines in mind and bake them into your preparation.

Be concise

There’s a big difference in the perceived quality of a 25-second answer vs. a 45-second answer. Getting straight to the point — while making sure you cover all the important material — conveys confidence.

More importantly, you need to maintain interest. As a former YC partner, I can testify to the fact that it gets tiring to sit through interviews for 8 straight days. You need to earn their attention, and the easiest way to do so is in direct, concise answers that don’t meander.

Convey your “3 things”

The interview goes by in a blur, and you don’t want to walk out having left out a major selling point of your company. To prevent this, write down three important things that you MUST convey.

If they don’t come up organically, guide the conversation in that direction.

For example, before my friend Ranidu founded Audius, he went through YC with Whale. It was a Q+A app, but the long-term vision was to expand to mobile video on Twitter. He made a point to guide the conversation towards the need for Twitter video, and shared the team’s early vision of a Q+A app being the first step to reaching the larger video market.

Don’t be defensive

You’re being interviewed by people who have evaluated hundreds or thousands of startups. When you get defensive about a question, you’ll come across as someone who can’t process constructive criticism.

Instead of being defensive, show that you’ve thought about it — or can do the homework to better answer it. A few weak answers are ok, but defensiveness will be seen as a negative trait that makes you ill-prepared for YC.

Have a lead speaker, but divide and conquer

One person on the team should take the lead on answering questions, but it’s hard for them to memorize every detail. Have a plan for “handing off” to certain team members on specific lines of questioning.

For example, the lead speaker should know the core metrics, but might not know all of them. Another cofounder can be solely responsible for memorizing every number in Mixpanel that might possibly be relevant. If it comes up, hand off to your metrics expert to concisely answer.

Don’t use jargon

Assume the YC partners don’t know all the acronyms and assumptions about your target market. Explain things to somebody who’s not an expert in your space — because more than likely, they aren’t. A good rule of thumb (and this applies to talking to any investor): you should be able to explain your product to someone who has zero industry context.


Be confident

My last tip to tie this all together: it’s ok to be nervous, but don’t be nervous about being nervous. Remember that you’re the expert in your business. You know much more about the space than the partners interviewing you.

Be confident in your answers, and walk into the room knowing that you understand this subject better than anyone else.

And some additional advice from myself and others who have gone through YC’s Demo Day


Photo Credit: TechCrunch

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Justin Kan is a renowned figure in Silicon Valley most known for co-founding Twitch, formerly, which sold to Amazon for $1 billion. Since he started his entrepreneurial journey in the Valley 15 years ago, Justin has founded 5 startups and invested in over 120 companies. Today, he’s the CEO and Co-founder of Atrium, a company that’s reimagining the delivery and consumption of professional services to allow founders to re-focus on their superpower. Previous to Atrium, Justin was a Partner at the preeminent startup accelerator Y Combinator. There, he mentored many founders and learned the value of having a startup community to exchange information and knowledge. During this time, Justin also realized that no founder succeeds alone - and that all first-time founders or serial entrepreneurs - need guidance and resources to compete in today’s increasingly saturated startup market. This realization helped inspire the inception of Atrium. Other companies Justin founded include Exec, an on-demand errand service (acquired by Handybook in 2014); Socialcam, a mobile app for sharing video (acquired by Autodesk in 2012); and Kiko, the first Ajax web calendar. Outside of his professional accomplishments and activities, Justin is an advocate for living consciously and being holistically healthy, especially emotionally. He often leads discussions about what it means to be a conscious individual and bring your whole self to any situation in or out of work. Justin graduated from Yale University with a Bachelor’s in Physics and Philosophy.

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