About

Sean Calarco

Fractional CTO and engineering advisor in Boston. I've scaled engineering at four high-growth companies and through two IPOs. Now I do that work for seed to Series B founders.

Sean Calarco, head and shoulders, in a dark suit jacket and white shirt.

My story

I'm a builder. I have been since I started making websites as a kid.

At Wayfair I joined before the IPO and helped build the delivery network from the ground up, as transportation engineering grew from fewer than ten people to over a hundred. I went on to lead platform engineering at The Predictive Index and Handshake, then founded Community Engineering at Reddit ahead of its IPO.

I've made my share of mistakes too. A lot of what I know, I learned the hard way, and I would rather a founder hear it from me than repeat it.

I started Calarco Consulting because so many startups have a great product but don't know how to scale the people, process and technology behind it. That's the gap I fill: too early for a full-time CTO, too far along to keep winging it.

How I work

  • Judgment over frameworks

    Every startup's problems look unique from the inside. I don't show up with a template. I bring pattern recognition from making these decisions myself, and apply it to what's actually in front of me.

  • Fix what's expensive to fix later

    Architecture, org design and hiring decisions are cheap to get right early and brutal to unwind once a team has grown around them. I focus on the calls that compound, not the ones that only feel urgent.

  • Outcomes, not recommendations

    A slide deck full of advice doesn't move anything by itself. I stay close enough to execution that what I recommend actually ships, and I'm accountable for the result.

  • Say the hard thing early

    The best engineering cultures I've built ran on direct, fast feedback: 5-why post-mortems, not blame. I bring the same directness to founders, even when it isn't what they want to hear.

What colleagues say

“What sets Sean apart is his ability to build healthy, balanced, and high-performing teams. He stood up a brand new org from scratch during our partnership, fast, without compromising on who he hired or what the team shipped. If you need someone who can build an engineering function from the ground up and keep it shipping while it grows, this is the rare person who has actually done it.”

Director of Product, Reddit. Sean's product partner for over two years.

“I had the chance to work directly with him on a large re-org, and was impressed with the level of trust his teams had in him: he kept things steady through big executive leadership changes. Sean was incredibly thoughtful in defining teams and management structures; he knows the questions to ask of product and the business to align engineering for long term success.”

VP of Product, Trust & Safety, Hinge. Worked with Sean at Reddit.

Career

  • Calarco ConsultingFounder and fractional CTO2026 to now
  • RedditDirector of Engineering, Core Experience and Moderation, then Head of Community Engineering2022 to 2026
  • HandshakeDirector of Engineering, Platform Services2022
  • The Predictive IndexHead of Platform Engineering2020 to 2022
  • WayfairSenior Software Engineer to Engineering Director, Middle Mile Technology2014 to 2020
Alongside
Board advisor on technology at Resupply, 2021 to 2023. Leadership coach to lead engineers, engineering managers and directors since 2020.
Education
Boston University, BA in Computer Science, minor in Philosophy.
Industries
Consumer, community, trust and safety, B2B, platform, HR tech and talent, supply chain and logistics, ecommerce.

Tell me where your team stands.

Tell me a little about your business. I'll reply personally and set up a free 30-minute call to get an honest read on what to do next. No sales pitch.

Start a conversation

Prefer email? Write to Sean@consultcalarco.com or message me on LinkedIn.