What I learned from interviewing at 2 early-stage YC startups (and many other companies)

A little while ago, I decided I was ready for a change. I was working in consulting on AI and data projects, which gave me a strong handle on both the technical and business sides of building systems. But I was craving something different. I wanted the full early-stage startup experience: a small, highly ambitious team working on hard problems with high stakes.

This search led me through numerous interview processes, including deep dives with two very early-stage YC startups. The experience was intense, demanding, and ultimately, incredibly informative. Here’s what I learned.

The YC Gauntlet: A Different Level of Intensity

The interviews with the two YC companies were unlike any others. They were long, rigorous, and designed to test every aspect of your being, not just your technical skills.

YC Company #1: The Eight-Interview Marathon

My first YC experience was a series of eight interviews. It started with what I’d call “energy screens.”

The initial calls were about cultural fit, but with a specific lens. My impression was that they were filtering for a particular personality type: high-energy, quick-thinking, and outgoing. You needed to be excited, talk fast, and project confidence. It felt like many candidates might get filtered out at this stage simply by not matching this specific vibe.

Then came the technical rounds:

• Live Coding: A standard LeetCode-style problem, but it also bled into topics like system design and coding styles.
• System Design: A classic “How would you build X?” interview, focusing on scalability and trade-offs.

After clearing these, I was invited for a mandatory on-site day in Berlin. They paid for everything—travel, hotel, and even a daily allowance, which was a nice touch.

The on-site day was built around one massive, end-to-end problem. I had to design a major new feature from scratch. This wasn’t just about APIs and database schemas. It involved:

• UX Design: How should the user interact with this?
• Data Modeling: How does this fit into their existing, complex data structure?
• Product Thinking: What are the customer’s real problems? What assumptions can I make? What are the constraints?

The key here was to constantly ask clarifying questions. They wanted to see if I could think on my feet, incorporate their feedback instantly, and weigh the pros and cons of different approaches in real-time. I consider myself a quick thinker, but this was a serious workout.

The afternoon involved a hands-on implementation of a small feature. It was a frontend task, which isn’t my strongest area. I got through it, but I didn’t feel I performed at my best.

A few days later, I got the rejection. They said it was a very close call. In hindsight, I learned I was the first candidate they were considering hiring from outside their personal network. Six months later, they still hadn’t hired anyone for the role. This told me their hiring bar was extraordinarily high, and being the first “outsider” is always a tougher position.

YC Company #2: The Palantir-Style Problem Solving

The second YC company, also very early-stage, had a similarly intense process, but with a few interesting twists.

It started with an asynchronous TypeScript coding challenge. The task itself was simple; you could have probably one-shotted it with an LLM. My instinct was to build a clean, simple solution fit for the task. In retrospect, this was a mistake. They weren’t testing if I could solve the problem; they were testing my depth of knowledge in TypeScript. They wanted to see advanced constructs, branded types, and a level of “over-engineering” to showcase my skills. I was able to clarify my reasoning in a follow-up call, but it was a key lesson.

The most unique stage was the problem-solving interview, influenced by the founders’ background at Palantir. They gave me a completely non-technical business problem and asked how I would achieve a specific target.

My approach was to start from first principles:

1. Gather data to understand the factors influencing the outcome.
2. Assemble a small team with domain experts.
3. Run iterative experiments to gather more data and test hypotheses.

What they were looking for was a systematic, data-driven approach and a clear bias for action. One piece of feedback I got was that I could have been even more systematic (e.g., “I’ll categorize the data I need into these areas…”) and that I should have pulled more information from the interviewer. Another lesson: always use the interviewer as a resource.

This was followed by a two-day on-site case study where I had to build a text-to-SQL-to-visualization feature. I worked late and got up early, sleeping about five hours. I felt good about the technical implementation, but I fumbled the final presentation. I presented it like a technical demo, but they were looking for a customer-facing demo. The lesson? Master the art of storytelling. I should have framed my solution with a story about a customer and how this feature solves their problem.

The outcome here was a “soft yes.” They wanted to hire me, but needed to onboard more customers first and couldn’t give a start date.

What About the Other Companies?

I also interviewed with a fast-growing (but not early-stage) startup, a consultancy, and a few mid-sized companies. The processes were more standard. There were still coding and system design interviews, but the intensity was lower.

However, the desired traits were consistent: they were all looking for driven, high-energy people with a bias for action. The YC companies just turned that dial up to 11 and demanded world-class technical skills to go along with it.

The Main Takeaways

Distilling all these experiences down, here’s what I learned.

1. High Energy is a Prerequisite. Especially at early-stage startups, they’re looking for people who bring energy to the room. They want proactive, confident, and articulate individuals who can think and react quickly.

2. Be an End-to-End Problem Owner. They aren’t hiring a “frontend dev” or a “backend dev.” They’re hiring someone who can take a vague customer problem, define it, design a solution (from the UI to the data model), build it, and understand the trade-offs along the way.

3. Storytelling is a Superpower. Being able to build something is only half the battle. You also need to be able to sell it. Whether in a demo or a system design interview, framing your ideas in a narrative about solving a real problem for a real user is incredibly powerful.

4. Ask More Questions. Interviewers aren’t just there to judge you; they’re a source of information. Clarify every assumption. Ask about constraints. Use their feedback to guide your thinking. This shows you’re collaborative and thoughtful.

5. Understand the Real Goal of the Task. My TypeScript challenge mistake taught me this. Was the goal to solve the problem efficiently, or was it to demonstrate mastery of a specific tool? Reading the context is crucial.

6. It’s a Marathon. An eight-interview process is a huge time commitment. I did it while working full-time, and it was draining. If you’re going to interview with these kinds of companies, be prepared and set aside the time and mental space for it.

The people at these top-tier YC startups are a potent combination of hardworking, extremely smart, and highly experienced. It’s an intimidating but also impressive environment. While I didn’t end up taking a role at either company, the process was one of the most valuable learning experiences of my career. It showed me the bar for top-tier startups and gave me a much clearer picture of what it takes to succeed there.