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  1. Lenny's Podcast: Product | Career | Growth
  2. Why experts writing AI evals is creating the fastest-growing companies in history | Brendan Foody (CEO of Mercor)
Why experts writing AI evals is creating the fastest-growing companies in history | Brendan Foody (CEO of Mercor)

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

Lenny's Podcast: Product | Career | Growth · Sep 18, 2025

We're in the era of evals. Mercor CEO Brendan Foody on hitting a $400M run rate in 16 months by supplying experts to improve AI models.

AI 'Evals' Are the New Product Requirement Documents for Models

The primary bottleneck in improving AI is no longer data or compute, but the creation of 'evals'—tests that measure a model's capabilities. These evals act as product requirement documents (PRDs) for researchers, defining what success looks like and guiding the training process.

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

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

Lenny's Podcast: Product | Career | Growth·5 months ago

Test Job Candidates' True Skill by Challenging Them to Build With AI Tools

Traditional hiring assessments that ban modern tools are obsolete. A better approach is to give candidates access to AI tools and ask them to complete a complex task in an hour. This tests their ability to leverage technology for productivity, not their ability to memorize information.

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

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

Lenny's Podcast: Product | Career | Growth·5 months ago

Mercor Reached $400M ARR with No Sales Team by Obsessing Over Flagship Customers

For over a year, Mercor focused 100% of its resources on product and customer experience, forgoing a sales team. This deep focus on flagship customers in a tight-knit industry (AI labs) generated powerful word-of-mouth that fueled its historic growth.

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

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

Lenny's Podcast: Product | Career | Growth·5 months ago

Mercor Grew to $400M ARR in 16 Months By Supplying Expert Humans to Train AI

The demand from AI labs for high-skilled professionals (engineers, lawyers, doctors) to create evals and training data created a historic business opportunity. Mercor capitalized on this by creating an expert labor marketplace, becoming the fastest-growing company in history.

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

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

Lenny's Podcast: Product | Career | Growth·5 months ago

Hypergrowth Startups Find PMF by Pivoting to Unexpected Market Pull, Not Forcing a Thesis

Founders can waste time trying to force an initial idea. The key is to remain open-minded and identify where the market is surprisingly easy to sell into. Mercor found hypergrowth by pivoting from general hiring to serving the intense, specific needs of AI labs.

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

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

Lenny's Podcast: Product | Career | Growth·5 months ago

A Few Elite Human Experts Drive Most of an AI Model's Performance Gains

In a group of 100 experts training an AI, the top 10% will often drive the majority of the model's improvement. This creates a power law dynamic where the ability to source and identify this elite talent becomes a key competitive moat for AI labs and data providers.

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

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

Lenny's Podcast: Product | Career | Growth·5 months ago

AI-Proof Jobs Are in Fields with Elastic Demand, Like Software Development

Instead of fearing job loss, focus on skills in industries with elastic demand. When AI makes workers 10x more productive in these fields (e.g., software), the market will demand 100x more output, increasing the need for skilled humans who can leverage AI.

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

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

Lenny's Podcast: Product | Career | Growth·5 months ago

AI Training Is Shifting from Human Feedback (RLHF) to Expert-Defined AI Feedback (RLAIF)

The frontier of AI training is moving beyond humans ranking model outputs (RLHF). Now, high-skilled experts create detailed success criteria (like rubrics or unit tests), which an AI then uses to provide feedback to the main model at scale, a process called RLAIF.

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

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

Lenny's Podcast: Product | Career | Growth·5 months ago