Cheat at Search Essentials: BM25 + Lexical

Hosted by Doug Turnbull

Tue, Jan 20, 2026

5:30 PM UTC (1 hour)

Virtual (Zoom)

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Go deeper with a course

'Relevant Search' masterclass
Doug Turnbull and Nick Zadrozny
View syllabus

What you'll learn

Basics of Information Retrieval

Learn the baseline that rules them all (BM25) and how it works

The importance of tokenization

How the simple decision of how to break up strings can make or break search

Cheat at semantic search without the vectors

How to achieve semantic search without vector search - and why you might prefer a lexical semantic approach

Why this topic matters

It's often said with chat interfaces and RAG, search has become the hard problem. Search has a long history and means more than vector databases. Let's learn how BM25 and similar techniques compliment your vector database. And why you might not want to always reach for embeddings. Part of "Cheat at Search - Essentials" intro to search course

You'll learn from

Doug Turnbull

Principal AI Engineer in Search

Doug leads search teams past the BS to find real opportunity in emerging search technologies. He’s enthusiastic about the evolving landscape, while staying mindful of the gap between marketing and reality. Good search strategy separates promising opportunities from dangerous sand traps. Doug helps teams find a clear, practical path forward.

He led machine-learning-driven search at Reddit and Shopify, served as CTO of OpenSource Connections, and co-authored Relevant Search and AI Powered Search.

Doug has trained and advised teams at the Wikimedia Foundation, Wayfair, and AWS, and created Quepid, SearchArray, and the Elasticsearch Learning to Rank plugin.

Previously at

Shopify.com
Reddit
Wikipedia
LexisNexis

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