Top 50 FAQs for Elasticsearch

1. What is Elasticsearch?

Ans:- Elasticsearch is an open-source, distributed search and analytics engine.

2. How does Elasticsearch differ from traditional databases?

Ans:- Elasticsearch is designed for fast, scalable full-text search and analysis, while traditional databases are often used for structured data storage.

3. What is the role of an index in Elasticsearch?

Ans:- An index in Elasticsearch is a collection of documents with similar characteristics.

4. How is data stored in Elasticsearch?

Ans:- Data in Elasticsearch is stored as JSON documents.

5. What is a node in Elasticsearch?

Ans:- A node is a single instance of Elasticsearch that participates in a cluster.

6. How does Elasticsearch achieve horizontal scalability?

Ans:- Elasticsearch achieves horizontal scalability by adding more nodes to a cluster.

7. What is a shard in Elasticsearch?

Ans:- A shard is a basic unit of data storage and retrieval in Elasticsearch.

8. What is the purpose of a replica in Elasticsearch?

Ans:- Replicas are copies of shards, providing fault tolerance and improving search performance.

9. How are queries executed in Elasticsearch?

Ans:- Queries in Elasticsearch are executed in a distributed manner across all nodes.

10. What is the Query DSL in Elasticsearch?

Ans:- The Query DSL (Domain-Specific Language) is a powerful syntax for defining queries in Elasticsearch.

11. Can Elasticsearch be used for structured data?

Ans:- While Elasticsearch is optimized for unstructured data, it can handle structured data as well.

12. How to install Elasticsearch?

Ans:- Installation instructions for Elasticsearch can be found on the official Elastic website.

13. What is the role of the Inverted Index in Elasticsearch?

Ans:- The Inverted Index is a data structure that allows for fast full-text searches.

14. How does Elasticsearch handle relevance scoring in search results?

Ans:- Elasticsearch uses TF-IDF (Term Frequency-Inverse Document Frequency) for relevance scoring.

15. What is a filter in Elasticsearch?

Ans:- A filter is a way to narrow down search results by applying specific criteria.

16. What are analyzers in Elasticsearch?

Ans:- Analyzers in Elasticsearch preprocess text during indexing and searching.

17. How does Elasticsearch handle real-time data indexing?

Ans:- Elasticsearch supports real-time indexing, allowing documents to be indexed and searched immediately.

18. What is the role of the Master Node in Elasticsearch?

Ans:- The Master Node is responsible for cluster-wide management tasks.

19. How to handle pagination in Elasticsearch?

Ans:- Pagination in Elasticsearch can be achieved using the from and size parameters in queries.

20. What is the purpose of the Refresh API in Elasticsearch?

Ans:- The Refresh API makes recently indexed documents available for search.

21. How to update documents in Elasticsearch?

Ans:- Documents in Elasticsearch can be updated using the Update API.

22. Can Elasticsearch be used for log analysis?

Ans:- Yes, Elasticsearch is commonly used for log analysis and monitoring.

23. What is the role of the _source field in Elasticsearch?

Ans:- The _source field stores the original JSON document of an indexed document.

24. How to handle full-text search in multiple fields?

Ans:- Multi-match queries or cross-field search can be used for searching across multiple fields.

25. What is the purpose of the Bulk API in Elasticsearch?

Ans:- The Bulk API allows for efficient batch processing of multiple index, update, or delete operations.

26. How to handle tokenization and stemming in Elasticsearch?

Ans:- Tokenization and stemming can be configured using custom analyzers.

27. What is the purpose of the Terms Aggregation in Elasticsearch?

Ans:- The Terms Aggregation is used for bucketing and analyzing data based on unique terms.

28. How does Elasticsearch handle data consistency in a distributed environment?

Ans:- Elasticsearch uses versioning and distributed consensus to maintain data consistency.

29. What is the role of the Cluster State in Elasticsearch?

Ans:- The Cluster State is a representation of the current state of the entire cluster.

30. How to secure Elasticsearch?

Ans:- Elasticsearch security features include authentication, authorization, and encryption.

31. What is the role of the Gateway module in Elasticsearch?

Ans:- The Gateway module is responsible for storing and retrieving persistent cluster metadata.

32. How to handle synonym expansion in Elasticsearch?

Ans:- Synonyms can be configured using the Synonym Token Filter.

33. What is the purpose of the Cat API in Elasticsearch?

Ans:- The Cat API provides human-readable information about nodes, indices, and more.

34. How to handle time-series data in Elasticsearch?

Ans:- Time-series data can be managed by using time-based indices and date filters.

35. What is the role of the Ingest Node in Elasticsearch?

Ans:- The Ingest Node allows for preprocessing documents before indexing.

36. How to handle nested documents in Elasticsearch?

Ans:- Nested documents can be indexed and queried using the Nested Query.

37. What is the role of the Task API in Elasticsearch?

Ans:- The Task API provides information about background tasks and their status.

38. How does Elasticsearch handle node discovery in a cluster?

Ans:- Nodes can discover each other through mechanisms like unicast or multicast discovery.

39. Can Elasticsearch be used for real-time analytics?

Ans:- Yes, Elasticsearch is suitable for real-time analytics on large datasets.

40. How to handle cross-cluster search in Elasticsearch?

Ans:- Cross-cluster search allows for searching across multiple Elasticsearch clusters.

41. What is the purpose of the Shrink Index API in Elasticsearch?

Ans:- The Shrink Index API allows for reducing the number of primary shards in an index.

42. How to handle index aliases in Elasticsearch?

Ans:- Index aliases provide a way to reference multiple indices with a single alias name.

43. What is the role of the Transform API in Elasticsearch?

Ans:- The Transform API is used for creating summary indices for analytics and reporting.

44. How to handle field collapsing in Elasticsearch?

Ans:- Field collapsing can be achieved using the Collapse Query.

45. What is the purpose of the Highlighting feature in Elasticsearch?

Ans:- Highlighting is used to emphasize matching terms in search results.

46. How to handle index templates in Elasticsearch?

Ans:- Index templates allow for defining settings and mappings for new indices.

47. What is the role of the Fielddata cache in Elasticsearch?

Ans:- The Fielddata cache is used to speed up aggregations and sorting.

48. How to handle parent-child relationships in Elasticsearch?

Ans:- Parent-child relationships can be modeled using the Parent-Child Join datatype.

49. What is the purpose of the _all field in Elasticsearch?

Ans:- The _all field is a special field that combines the values of all other fields for search purposes.

50. How to handle index lifecycle management (ILM) in Elasticsearch?

Ans:- ILM allows for defining policies to manage the lifecycle of indices, including rollover and deletion.