# Amazon OpenSearch Service

> Managed search engine on AWS, for site search boxes and digging through logs.

- Level: Intermediate
- Topics: AWS, Data
- URL: https://tidbit.legios.com.ar/amazon-opensearch-service/
- In Spanish: [Amazon OpenSearch Service](https://tidbit.legios.com.ar/es/amazon-opensearch-service/)

**OpenSearch** is an open source search and analytics engine, the technology behind the search box of many websites. **Amazon OpenSearch Service** runs it for you on AWS: you get a cluster that stays patched and backed up, and you send it documents to make searchable. It grew out of Elasticsearch, and the service was called Amazon Elasticsearch Service until 2021.

Its core is an **inverted index**: for every word, a list of the documents where it appears, like the index at the back of a book. That is why it can search millions of product descriptions for "red running shoes" in milliseconds, tolerate typos, and rank the results by relevance, things a regular database does poorly.

The other big use is logs. Apps and servers produce endless lines of text, and teams send them to OpenSearch to search for an error message, count failures per minute, or build charts in **OpenSearch Dashboards**, its visual tool. More recently it is also used for vector search, finding documents by meaning rather than exact words, which is a common piece of RAG systems. A serverless option scales capacity without managing a cluster.

## An analogy

The index at the back of a giant book. Instead of reading every page to find "volcano", you look it up and jump straight to pages 12, 87 and 341, the most relevant first.

## Keep in mind

- Managed OpenSearch, the open source descendant of Elasticsearch.
- Uses an inverted index for fast, typo-tolerant, ranked full-text search.
- Widely used to search and chart application logs.
- Also supports vector search for finding text by meaning.

## Go deeper

- [What is Amazon OpenSearch Service? (official docs)](https://docs.aws.amazon.com/opensearch-service/latest/developerguide/what-is.html)
- [What is OpenSearch? (AWS)](https://aws.amazon.com/what-is/opensearch/)
- [OpenSearch on Wikipedia](https://en.wikipedia.org/wiki/OpenSearch_(software))

## Related terms

- [Open source](https://tidbit.legios.com.ar/open-source/): Software whose code anyone can read, use, change and share.
- [Database index](https://tidbit.legios.com.ar/database-index/): A sorted shortcut that lets a database find rows without reading the whole table.
- [Database](https://tidbit.legios.com.ar/database/): An organized store of data that programs can search and update safely.
- [Server](https://tidbit.legios.com.ar/server/): A computer whose job is to answer requests from other computers, all day, every day.
- [RAG](https://tidbit.legios.com.ar/rag/): Let the model look things up in your documents before it answers.
- [Serverless](https://tidbit.legios.com.ar/serverless/): Code that runs only when called; you never see or manage the server.