Doron Segal Co-founder & CTO, Per Diem — Y Combinator W21

Founder advice from someone who has had to own the outcome.

I coach early founders through product, pricing, fundraising, hiring, and technical risk. YC W21. Two startups founded and acquired. One platform I still run today, from the first commit to real customers using it every morning.

15+
Years shipping
3
Companies founded
2
Acquisitions
W21
YC batch

Operator, not commentator

Young founders do not need more frameworks. They need better calls.

Noise

  • Generic advice that sounds smart and changes nothing.
  • Recommendations with no downside for the person making them.
  • A plan that ignores customers, cash, and founder energy.

Signal

  • A clear next move tied to customers, revenue, or risk.
  • Straight feedback from someone who has raised, shipped, scaled, and missed before.
  • Hands-on help when the answer is not another meeting.

Testimonials

What it's like to work with me.

Doron has the rare founder-engineer ability to turn messy ideas into working products without losing sight of the people using them. He brings speed, taste, and real technical judgment to every conversation.
Yonatan K.
Working with Doron feels like having a CTO, product strategist, and builder in the same room. He asks sharp questions, moves fast, and keeps the work grounded in what actually matters.
Sarah M.
Doron doesn’t just write code; he creates momentum. He can take an ambiguous problem, cut through the noise, and ship something clean, useful, and thoughtfully built.
Gill S.
What stands out about Doron is his balance of curiosity and execution. He explores deeply, but when it’s time to build, he becomes practical, focused, and incredibly effective.
James T.
Doron explains complex technical ideas in a way that makes them feel approachable. Whether he’s discussing machine learning, product architecture, or startup strategy, he makes people smarter around him.
Ravit B.
As a founder and technical leader, Doron brings calm clarity to high-pressure work. He sees both the system and the user, which makes his decisions unusually strong.
Hadar M.
Doron is a builder in the best sense: hands-on, thoughtful, and allergic to unnecessary complexity. He brings clean engineering, product intuition, and a genuinely optimistic energy to the work.
Michael D.
Doron introduced AI into our business end to end — today 80% of our operations run automated, and the team finally has room to tackle the next big thing.
Daniel P.

Services

Three ways I help founders move.

Every engagement is shaped around the stage you are in: first customer, product-market fit, or the operating problems that show up once growth starts.

01 Founder Operating ReviewA focused review of product, customer signal, pricing, fundraising story, team, and technical risk — with the next decisions made explicit. 30 days
02 Zero to First CustomerWeekly coaching for founders turning an idea into something someone will pay for, without hiding in product work for a year. Coaching
03 Fractional CTO / Builder-in-ResidenceHands-on technical leadership when the product has to ship, the first engineers need a bar, or a decision is about to get expensive. Ongoing

How I work

Four rules I do not bend.

Ship

Ship to learn

A small thing in production teaches more than a quarter of planning. Launch fast, then let real usage pick the roadmap.

Types

Types and security are defaults

Strict typing, tenant-scoped queries, secrets in a vault. Not a later phase. It is how you keep moving fast for longer.

Ownership

Empower teams, do not direct them

Clear ownership beats detailed process. I set the bar and the context, then get out of the way.

Business

Engineering serves the business

Elegant architecture that moves no business number is a hobby. I optimize for the number.

Resources

Two field guides. Free, no email required.

Written from running the thing, not from advising on it.

8 pages · PDF

Zero to First Customer

Idea to first paying customer. The sequence I would run again, and the five ways I have watched it fail.

Download PDF
8 pages · PDF

After It Works

Scaling a product without breaking it. What fails first, in what order, and what it costs to fix it late.

Download PDF

Background

Twenty years of shipping, mostly under someone else's deadline.

PER DIEM · YC W21Co-founder and CTO. Square-native ordering, loyalty, and customer engagement for brick-and-mortar merchants.
SAILDRONEFounding engineer.
OPENTABLEEngineering manager. Owned availability search and drove the move to containers.
BEATS MUSIC → APPLEPlatform lead for auth, users, and artist APIs, through the launch and the acquisition.
Two earlier startupsTechnical co-founder of both. Both acquired.
EducationExecutive MBA, Ben-Gurion University. High-Impact Leadership, UC Berkeley Haas.

For engineers

Career advice from the person who reads the resume.

I hire engineers and I sit on the other side of the loop. Separate from client work, I keep a few slots each month for individual engineers.

AI

What AI actually changed about your job

Which parts of the work became commodity, which became more valuable, and what to start building evidence in now rather than in two years.

Loop

The long interview loop

System design, take-homes, five rounds. How to prepare for each stage, and how to read what the company is actually testing.

Level

Leveling, scope, and the IC or manager fork

What separates senior from staff in practice, when management is the wrong move, and how scope really gets handed out.

I also work one-on-one as a coach — leveling, the interview loop, and landing the job you actually want.

Contact

Tell me the problem. Not the tech stack.

One call, no deck. If I am not the right person for it, I will say so and point you at someone who is.