elasticsearch
2 free lessons tagged elasticsearch across Computer Science. Each one is a short sequence of focused steps with narration and a five-question quiz at the end — take them in any order, no signup required.
BM25: How Lexical Relevance Is Actually Computed
Matching finds candidates; scoring orders them, and the ordering is the product. This lesson builds BM25, the default ranking function of Lucene, Elasticsearch and OpenSearch, from its three ingredients: rare terms count more, repeated terms saturate, and long documents get discounted. With the formula, the two tuning knobs, and the saturation curve computed by hand.
The Inverted Index, and Why Analysis Decides Everything
Search does not scan documents; it looks up precomputed answers. This lesson builds the inverted index from first principles, then covers the pipeline that feeds it: tokenization, normalisation, stemming and synonyms, and why an analysis mistake made at index time cannot be fixed at query time. Includes the classic failure where a product SKU becomes unfindable.