How search engines find things
On This Lesson 4 topics
This lesson is planned. The outline below lists the topics it will cover. The full lesson has not been published yet.
In this lesson
explain the inverted index and why full-text search is fast.
Planned topics
- Normal index: document → words. Inverted index: word → list of documents containing it.
- A query looks up each word and combines the lists (AND/OR), so it does not scan every document.
- Engines (Lucene-based: OpenSearch, Elasticsearch) split an index into shards for scale and replicas for availability.
- Search is near-real-time: a document becomes searchable after a refresh (about a second by default; verify).
- A search engine is a derived view of data, not a database of record.
Draft outline details
Demonstration
| Term | Documents |
|---|---|
| red | 1, 3 |
| shoe | 1, 2, 3 |
| leather | 2 |
Query red shoe intersects lists to find docs 1 and 3.
Check your understanding
Why is an inverted index fast?
Show answer
It looks up words directly instead of scanning all documents.
Practice
Apply this lesson with the module's lab, exercises and quiz.
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