Lenny's Podcast: Product | Career | Growth · Lenny Rachitsky

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

·1 hr 7 min·5 clips

Brendan Foody shares how Mercor grew from $1 to $400 million in revenue in just 16 months.

Lenny Rachitsky opens with remarkable statistics about Mercor: the company grew from $1 to $400 million in revenue run rate in 16 months, which he describes as the fastest ascent in history, subsequently revised to $1 to $500 million in 17 months. Brendan Foody, CEO and co-founder, is described as the youngest unicorn founder ever. Mercor connects AI labs and AI companies with expert human evaluators who help train AI models, essentially operating as a labor marketplace for the specific kind of high-quality human judgment that frontier AI labs need to improve their models. Foody explains the core insight that led to Mercor: AI labs are constrained in their ability to improve models not by compute or data in the traditional sense, but by their ability to measure what success looks like. That measurement requires humans with genuine domain expertise who can evaluate model outputs with the kind of nuanced judgment that distinguishes excellent from merely adequate. Mercor has never had a customer churn, and its net revenue retention is over 1,600%, meaning customers spend dramatically more over time rather than leaving. Foody describes how Mercor finds and vets evaluators, building a marketplace of extraordinary professionals across domains from medicine to law to mathematics to software engineering. The episode covers what Foody sees as the broader implication of his company's existence: that human judgment is not being replaced by AI but is instead being industrialized as the essential input for making AI better, with the possibility that the entire economy eventually becomes an RL environment with humans continuously providing training signal. Foody discusses the earliest days of the company, how he identified the opportunity, and the specific product-market fit signals that told him Mercor had found something real. The tone is energetic and future-oriented, with Rachitsky probing for specific metrics and mechanisms. The audience is founders and investors interested in the business infrastructure around frontier AI.

As heard by us

Mercor is framed as a fast-growing answer to the messier side of AI evals and hiring.

Brendan Foody presents Mercor as a bet that AI labs will pay for exceptional people who can help measure model capability, while the hiring process itself still leans heavily on manual sorting.

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Why you'd press play

You get a sharp read on why AI evals are suddenly the business worth chasing.

Read the full recommendation in PlayNext →

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