ElasticSearch Interview Questions: ElasticSearch is a highly scalable open-source full-text search engine.
Q: What is ElasticSearch?
ElasticSearch is a Search Engine based on Apache Lucene that supports FullText Search.

ElasticSearch can be used to search different kinds of documents that provide scalable search, multi-tenancy, and real-time search.

ElasticSearch is developed in Java (Developed By - Shay Banon) and is released as open source under the terms of the Apache License.

Q: How to Install ElasticSearch?
Install ElasticSearch on Linux:
curl -L -O https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-7.3.1-linux-x86_64.tar.gz tar -xzvf elasticsearch-7.3.1-linux-x86_64.tar.gz cd elasticsearch-7.3.1 ./bin/elasticsearch
Install ElasticSearch on Windows:

Steps to Install ElasticSearch on Windows:

  1. Download the Elasticsearch 7.3.1 Windows zip file from the ElasticSearch Download page.
  2. Extract the contents of the zip file to a directory on your computer.(e.g. - C:\ElasticSearch.)
  3. Open Command Prompt as an Administrator and navigate to the directory that contains the extracted files
    cd C:\ElasticSearch\elasticsearch-7.3.1
  4. Start Elasticsearch:
    5. bin\elasticsearch.bat

For other OS you may follow ElasticSearch Official Guide

To test that the Elasticsearch is up and running, try sending an HTTP GET request on port 9200.

curl http://127.0.0.1:9200
Q: What is Query Language in ElasticSearch?

ElasticSearch uses apache lucene query language, which is called Query DSL.

Q: What is Inverted Index in ElasticSearch?

ElasticSearch uses a structure called an inverted index, which is designed to allow very fast full-text searches. An inverted index consists of a list of all the unique words that appear in any document, and for each word, a list of the documents in which it appears.

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Q: What is a Tokenizer in ElasticSearch?

In simple word - Tokenizers break down a string into stream of tokens.

Q: Does ElasticSearch have a schema?

Yes, ElasticSearch can have a schema.

Q: What are the advantages of ElasticSearch?

Following are the advantages of ElasticSearch:

  1. ElasticSearch is compatible on any platform.
  2. ElasticSearch cluster is distributed, scalable and most important easy to integrate.
  3. ElasticSearch REST uses JSON objects, works perfectly with different programming languages.
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