Building Brave: Private Search, One AI Layer at a Time with Josep M. Pujol

15 Jun 2024 · 85 min
"The Cognitive Revolution"

15 Jun 2024 · 85 min

0:00

In this episode of The Cognitive Revolution, host Nathan Labenz interviews Josep M. Pujol, Chief of Search at Brave, to unpack the technical, privacy, and business dimensions of Brave Search. The conversation begins with an overview of Brave’s mission—a privacy‑first browser and search engine founded by Brian Bondi and Brendan Eich—and how the search team, a small group of about 20 engineers, builds a product that handles over a million queries per hour. Pujol explains Brave’s data collection strategy via the opt‑in Web Discovery Project, emphasizing record unlinkability and anonymous, per‑page signals rather than full browsing histories. The index is constructed by fetching URLs that users actually visit, dramatically reducing noise compared to blind crawling and resulting in an index roughly one‑tenth the size of Google’s while achieving 99.9% recall. The architecture relies on a hybrid retrieval stack: dense transformer‑based embeddings (384‑dimensional vectors), sparse 16k‑dimensional bit vectors for literal matching, and massive query‑log similarity tables (over 9 billion unique queries). Multiple models are added incrementally, forming an ensemble that is weighted by a gradient‑descent tree ranker. Hardware advances—large‑memory servers, petabyte‑scale NVMe storage, and GPU clusters (e.g., 20 A100s)—enable fast embedding generation (≈2 ms per page) and scalable indexing. Pujol discusses model upgrades: LLM summarizers are swapped relatively easily, but core embeddings are treated as immutable because re‑embedding the entire corpus is costly; instead new embeddings are added and ensembled. Evaluation combines high‑quality human raters, automated metrics (NDCG, intersection with competitor results), and continuous query‑log analysis, with safeguards against over‑fitting. The summarizer lacks a formal “constitution” and is guided by human taste and iterative fine‑tuning. Business considerations include the cost of running LLMs at scale (30 M daily queries, up to 4 k tokens per query) and the decision to self‑host infrastructure rather than rely on third‑party APIs. Brave offers a public Search API as a privacy‑preserving alternative to Google’s limited custom search and Microsoft’s Bing API. The API is priced at $9 per 1,000 queries for the summarizer‑enabled tier—significantly cheaper than Bing’s comparable $25 per 1,000—while returning richer results with multiple snippets and structured data. The API’s flexible terms (no attribution required, ability to mix results) make it attractive for developers building RAG pipelines, LLM grounding, or custom search experiences. Pujol mentions several use‑case categories (RAG, foundational model training, LLM output verification) and points to community demos such as a Perplexity‑style clone built with LangChain, Brave Search, and Groq. The user base is globally distributed (≈30% US, strong European presence) with similar usage patterns across regions. Throughout, Pujol stresses the importance of privacy, incremental engineering, and pragmatic trade‑offs over hype, and expresses satisfaction that Brave is becoming a viable alternative to Bing for customers seeking a privacy‑first search solution.

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