Why experts writing AI evals is creating the fastest-growing companies in history

Lenny's Podcast: Product | Career | Growth

Why experts writing AI evals is creating the fastest-growing companies in history | Brendan Foody (CEO of Mercor)

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Why experts writing AI evals is creating the fastest-growing companies in history | Brendan Foody (CEO of Mercor)

Lenny Rachitsky

Sep 18, 2025

∙ Paid

Watch on YouTube →

Also on Spotify and Apple Podcasts

Jump to the best parts:

(05:38) → Why we’re entering the “era of evals”: Why evaluations aren’t just technical benchmarks, but the new PRDs and even the sales collateral for AI companies
(09:26) → From $0 to $400M in 16 months: The wild origin story of how a group of 21-year-olds stumbled onto AI’s biggest bottleneck
(38:58) → Building the fastest-growing company ever: The core tenets that fueled Mercor’s record-breaking growth

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Brendan Foody is the CEO and co-founder of Mercor, the fastest-growing company in history to go from $1M to $500M in revenue (in just 17 months!). At 22, he is also the youngest American unicorn founder ever. Mercor works with 6 of the Magnificent 7 and all top 5 AI labs to help them hire experts to create evaluations and training data that improve their models. In this conversation, Brendan explains why evals have become the critical bottleneck for AI progress, how he discovered this massive opportunity, and what the future of work might look like in an AI-driven economy.

What you’ll learn:

Why evals are becoming the primary bottleneck for AI progress and what this means for AI startups
How Mercor grew to $500M revenue in 17 months (fastest in history)
Brendan’s meeting with xAI that changed his company’s trajectory
Which skills and jobs will remain most valuable as AI continues to advance (hint: jobs with “elastic” demand)
Why Brendan believes AGI and superintelligence are not happening anytime soon
The three unique core values that drove Mercor’s success
How Harvard Lampoon writers are making Claude funnier

Where to find Brendan Foody:

• X: https://x.com/BrendanFoody

• LinkedIn: https://www.linkedin.com/in/brendan-foody-2995ab10b/

In this episode, we cover:

(00:00) Introduction to Brendan Foody and Mercor

(05:38) The “era of evals”

(09:26) Understanding the AI training landscape

(17:10) The future of work and AI

(25:54) The evolution of labor markets

(29:55) Understanding how AI models are trained

(38:58) Building Mercor

(53:27) Lessons from past ventures

(56:55) The future of AI and model improvement

(01:00:41) His personal use of AI and final thoughts

Watch or listen now:
YouTube • Spotify • Apple Podcasts

Referenced:

• Mercor: https://mercor.com/

• No Priors Ep. 110 | With Mercor CEO and Co-Founder Brendan Foody: https://www.youtube.com/watch?v=vnkVYLhGd_s

• Sarah Guo’s post on X about evals: https://x.com/saranormous/status/1948565353514316021

• Cursor: https://cursor.com/

• The rise of Cursor: The $300M ARR AI tool that engineers can’t stop using | Michael Truell (co-founder and CEO): https://www.lennysnewsletter.com/p/the-rise-of-cursor-michael-truell

• Lovable: https://lovable.dev/

• Building Lovable: $10M ARR in 60 days with 15 people | Anton Osika (CEO and co-founder): https://www.lennysnewsletter.com/p/building-lovable-anton-osika

• Bolt: https://bolt.new/

• Inside Bolt: From near-death to ~$40m ARR in 5 months—one of the fastest-growing products in history | Eric Simons (founder and CEO of StackBlitz): https://www.lennysnewsletter.com/p/inside-bolt-eric-simons

• Replit: https://replit.com/

• Behind the product: Replit | Amjad Masad (co-founder and CEO): https://www.lennysnewsletter.com/p/behind-the-product-replit-amjad-masad

• v0: https://v0.app/

•Everyone’s an engineer now: Inside v0’s mission to create a hundred million builders | Guillermo Rauch (founder and CEO of Vercel, creators of v0 and Next.js): https://www.lennysnewsletter.com/p/everyones-an-engineer-now-guillermo-rauch

• Handshake: https://joinhandshake.com/

• Inside the expert network training every frontier AI model | Garrett Lord (Handshake CEO): https://www.lennysnewsletter.com/p/inside-handshake-garrett-lord

• Scale: https://scale.com/

• Surge: https://www.surgehq.ai/

• Andrej Karpathy on X: https://x.com/karpathy

• Anthropic co-founder on quitting OpenAI, AGI predictions, $100M talent wars, 20% unemployment, and the nightmare scenarios keeping him up at night | Ben Mann: https://www.lennysnewsletter.com/p/anthropic-co-founder-benjamin-mann

• Amber Yang’s post on X about creating RL training data: https://x.com/theamberyang/status/1952462320174600385

• Codex: https://openai.com/codex/

• Claude code: https://www.anthropic.com/claude-code

• Neuralink: https://neuralink.com/

• Alphasights: https://www.alphasights.com/

• GLG: https://glginsights.com/

• The Harvard Lampoon: https://www.harvardlampoon.com/

• Greg Brockman’s post on X about evals: https://x.com/gdb/status/1733553161884127435

• Tesla: https://www.tesla.com/

• xAI: https://x.ai/

• General Catalyst: https://www.generalcatalyst.com/

• Benchmark: https://www.benchmark.com/