Popular 30 Elasticsearch Interview Questions and Answers[Recent-2020] for Beginners/Freshers

Table of Contents

Elasticsearch Interview Questions and Answers

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1. Which Engine is used in Elasticsearch ?

Ans. Lucene Engine.

2. Is Elasticsearch document based or Schema/Table based ?

Ans. Document Based

3. What is the meaning of Near Real Time in Elasticsearch ?

Ans. It means as soon as the data is imported in the Elasticsearch, it will becomes searchable in almost no time. This
features makes it almost a Real Time Platform.

4. What is Index ?

Ans. It is a collection of multiple categories of Documents which share a similar characteristics.

5. On what basis an Index operations like search,delete and update will be performed against its documents ?

Ans. Index Operations will be performed based on Index Name.

6. What is Cluster ?

Ans. It is collection of nodes available in the distributed environment across which the data is saved.

7. When Elasticsearch create shards ?

Ans. When index size becomes big enough, then elasticsearch divide index into multiple shards. Each shards will then
behave as independent fully functional Index.

8. What is the query to check Elasticsearch Cluster status ?

Ans. curl http://localhost:9200/_cluster/health?pretty

9. What is the query to check Elasticsearch Indices ?

Ans. curl http://localhost:9200/_cat/indices?pretty

10. What is the name of Elasticsearch configuration file ?

Ans. elasticsearch.yml

11. What are different types of API in Elasticsearch ?

Ans.Few of the APIs are :-

Document API
Index API
Search API
Cluster API
Aggregation API

12. What are different types of Document API ?

Ans. Two types of API are there:-

Single Document API
Multi Document API

13. What are different Single Document API ?

Ans. Different single document APIs are:-

Index API
Get API
Update API
Delete API

14. What are different Multiple document API ?

Ans. Few of the APIs are:-

Multi GET API
Bulk API
Delete by Query API
Update by Query API
Reindex API

15. How to check all unassigned shards ?

Ans. curl -XGET http://<elastichost>:9200/_cat/shards | grep UNASSIGNED | awk {'print $1'}

16. How to delete all unassigned shards ?

Ans. curl -XGET http://<elastichost>:9200/_cat/shards | grep UNASSIGNED | awk {'print $1'} | xargs -i curl -XDELETE "http://<elastichost>:9200/{}"

17. Which is the latest version of Elasticsearch currently available ?

Ans. Elasticsearch 7.6.2

18. What are different types of Tokenizers supported in Elasticsearch ?

Ans. Three types of Tokenizers are supported:-

Word-Oriented Tokenizer
Partial Word Tokenizer
Structured Text Tokenizer

19. What is the query to check document exists or not ?

Ans. curl -i -XHEAD http://localhost:9200/<document_name>

20. Which Scripting Language get used in Elasticsearch to write custom scripts ?

Ans. Groovy Scripting Language

21. What will you do when a conflict occurs during document partial update ?

Ans. You need to reattempt the update

22. Which parameter usually allows us to use Optimistic Concurrency Control while updating the document ?

Ans. Version parameter

23. Which API you will use to retrieve multiple documents from Elasticsearch ?

Ans. Multi-get or mget api

24. Which formula elasticsearch uses to determine which shard a document belongs to ?

Ans. shard = hash(routing) % number_of_primary_shards

25. How to return all documents that contains some word "xyz" ?

Ans. GET /_search?q=xyz

26. How to request 7 results per page from pages 1 to 3 ?

Ans. Below is the query:-

GET /_search?size=7
GET /_search?size=7&from=14
GET /_search?size=7&from=14

27. Which parameter you should add into the query when response time is more important than the results ?

Ans. timeout parameter

28. What is Inverted Index ?

Ans. It is a structure in Elasticsearch which allows us to do very fast full-text searches.

29. What are different types of data in Elasticsearch ?

Ans. It can be broadly divided into two types:-

Exact Values
Full Text

30. What is Search Lite ?

Ans. It is a query string search tool useful for Adhoc queries through command line.

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