AfterQuery Becomes Y Combinator’s Fastest Unicorn, Achieving a Valuation of $3.2 Billion

The AI training-data startup AfterQuery has reportedly secured funding that has boosted its valuation to $3.2 billion, just five months after disclosing its $30 million Series A funding round at a $300 million valuation in April.

This signifies a growth of over 10x in less than six months and, according to Y Combinator partner Gustaf Alströmer, represents the quickest rise to unicorn status for any startup in the accelerator’s history. The founders of AfterQuery, who are currently 22 and 23 years old, were part of Y Combinator’s Winter 2025 cohort just 18 months ago.

In April, the San Francisco-based company revealed an annualized revenue run rate of $100 million and mentioned that it is working with numerous leading laboratories. Among its clientele are notable firms such as Nvidia, Legora, and the Korean AI lab Motif Technologies.

AfterQuery is part of a new generation of startups, inspired by Mercor and Scale, that collaborate with knowledge professionals, including doctors and lawyers, for model training. Rather than merely ensuring precise answers, AfterQuery emphasizes training models and agents to function like experienced professionals to complete tasks—described by the company as “encoding the patterns, decisions, and reasoning of the world’s best practitioners.”

Forbes was the first to report on this funding round. AfterQuery did not respond to requests for immediate comment.