Skip to the document
Madhuopen lab
Outcome School · Retrieval and RAG21 min read

by Amit Shekhar · 8 June 2026

How does a Reranker work?

How a Reranker works. We will also see where it sits in a search and RAG pipeline, why we need it, and how it makes our answers more accurate.

4,129 words#ai#system-design4 recall cards

How does a Reranker work?
Read on Outcome School ↗then come back to lock it in
Before you read, guess

Where does the Reranker live in a real system?

Ten seconds, a guess, then read — a wrong guess still makes the answer stick.

What this article covers

  1. What is a Reranker
  2. Where a Reranker sits in a search / RAG pipeline
  3. The two-stage retrieval idea
  4. Why first-stage retrieval is fast but not precise
  5. Bi-encoder vs Cross-encoder
  6. How a Reranker scores documents step by step
  7. The accuracy vs latency and cost trade-off
  8. Late-interaction models like ColBERT
  9. Real examples of Rerankers
  10. Why Rerankers matter for RAG

The article lives on outcomeschool.com. Read it there, then come back: the tutor in the margin has read it and will answer questions, and the questions below check what stayed.

Before you go

In one sentence, what was this chapter about?

From memory, without scrolling up. Writing it is what makes it yours; the grade is only to show you what you had.

How sure?