Sample Questions for the Y Combinator Interview

Liron Shapira
3 min readOct 24, 2018

I faced the infamous Y Combinator interview for my company Relationship Hero (YC S17). For 10 surreal minutes, the YC partners shotgunned questions at me and my cofounders and interrupted us a few times. Afterwards, when the partner called, here’s what they said:

We were skeptical that this could be a big market, but you guys convinced us.

Below is our 100% proven list of questions which we used in mock interviews to prepare.

What are you making?

Some variant of “what are you making”, “what are you working on”, or “what are you going to build” is a common first interview question.

Your Numbers

Know your numbers cold.

  • How many users have ever engaged
  • How many currently active users
  • Total revenue
  • Total costs, fixed and marginal
  • Acquisition funnel conversion rate
  • Customer acquisition cost
  • Growth rates of all of the above

Value Prop

  • Who needs what you’re making?
  • What’s new about what you make?
  • What are the top things users want?
  • What are your users doing now?
  • How does your product work in more detail?

Market Size

  • How many people are in your target market?
  • How many $B is the market?
  • How fast is the market growing?
  • Who are your competitors? Who might become competitors?
  • Which competition do you fear most?
  • How many users do your competitors have?
  • How much are your competitors making?
  • How much time and money do users in your target market waste before switching to your product/service?
  • What are some trends in your target market, and related markets?

User Acquisition

  • Who is going to be your first paying customer / who was your first paying customer?
  • How do you get users?
  • How do users know they need this?
  • What exactly makes you different from existing options?
  • How will users find out about you?
  • What makes new users try you?
  • What makes new users reluctant to try you?
  • How will you overcome that resistance?


  • What’s an impressive thing you have done?
  • Tell us something surprising that has happened.
  • What’s the biggest mistake you have made?

Founder-Market Fit

  • Why did you choose this idea?
  • Why are you uniquely qualified to work on this?
  • Why do you want to dedicate your life to working on this?

Growth Potential

  • How will you make money?
  • How much money could you make per year?
  • How does this become a billion-dollar company?
  • If your startup succeeds, what additional areas might you be able to expand into?


  • Why did your team get together?
  • Who is “the boss”?
  • Who will be your next hire?
  • How do we know your team will stick together?


  • What’s the rocket science here?
  • What part of this are you going to build first?
  • What have you learned so far from working on this idea?
  • Why isn’t someone already doing this?
  • What are the key things about your field that outsiders don’t understand?
  • What keeps you up at night?
  • What obstacles will you face and how will you overcome them?
  • Six months from now, what’s going to be your biggest problem?
  • What’s the funniest thing that has happened to you?
  • Are you open to changing your idea?
  • Have you considered [some twist on your idea]?

Finally, remember that a lot of questions aren’t listed here because they’ll be specific to your company. In the Relationship Hero interview, we got asked how we go about training relationship coaches, what happens when the coaches deal with sensitive or morally ambiguous situations, and whether we ourselves were in relationships.

[Updated 2022] If you’re currently in the pre-revenue stage, I write a blog called Bloated MVP explaining why you’ve probably been wasting your last few months of effort. I like giving founders free advice and potentially angel investing, so please email me or hit me up on Twitter to get my advice or feedback about anything.