Top 30 ElasticSearch Interview Questions for Freshers with answers

ElasticSearch Interview Questions: The Elastic Stack has become an integral part of modern data management and analysis. Whether you’re a seasoned professional or preparing for an Elastic interview, understanding the key concepts and technical aspects is crucial. In this comprehensive guide, we’ll explore the top 30 Elastic interview questions and provide detailed answers to help you ace your interview.

Elasticsearch is a powerful, open-source, distributed search engine built on Apache Lucene. It provides a scalable solution for indexing and searching various types of data, offering real-time search capabilities. With a RESTful API, it seamlessly integrates with other tools like Logstash and Kibana in the Elastic Stack, making it a popular choice for organizations managing large volumes of data. Elasticsearch is widely used for its flexibility, high availability, and robust search functionality in diverse applications, ranging from log analysis to business intelligence.

Why Elasticsearch is better than database

Elasticsearch and traditional databases serve different purposes, and the choice between them depends on the specific use case. Here are reasons why Elasticsearch might be preferred over traditional databases in certain scenarios:

  1. Full-Text Search Capability: Elasticsearch excels in full-text search, making it efficient for applications requiring powerful and flexible search functionality. Traditional databases may not offer the same level of search performance.
  2. Scalability: Elasticsearch is designed for horizontal scalability, allowing you to easily add more nodes to a cluster to handle increased data volumes. Traditional databases might require more complex scaling solutions.
  3. Real-Time Data: Elasticsearch provides real-time indexing and searching, making it suitable for applications where data is constantly changing, such as log analysis or monitoring. Traditional databases might have delays in reflecting real-time changes.
  4. Distributed and Fault-Tolerant: Elasticsearch is distributed by nature, providing fault tolerance and high availability. Traditional databases may require additional configurations for distributed setups.
  5. Schema-Free: Elasticsearch is schema-less, allowing for dynamic mapping of fields. This flexibility is advantageous for handling diverse and evolving data structures. Traditional databases often require a predefined schema.
  6. Rich Query Language: Elasticsearch offers a powerful Query DSL (Domain-Specific Language) for constructing complex queries, enabling advanced search capabilities. Traditional databases might not provide as extensive a query language for search operations.
  7. Text Analysis and Tokenization: Elasticsearch includes built-in text analysis and tokenization features, making it well-suited for natural language processing and linguistic analysis. Traditional databases may lack specialized features for such tasks.

It’s important to note that while Elasticsearch is excellent for certain use cases like search and analytics, traditional databases excel in transactional applications where structured data, ACID compliance, and relational models are critical. The choice between them depends on the specific requirements of the application and the nature of the data being managed. Many modern applications use both types of databases in combination to leverage their respective strengths.

Elasticsearch advantages

Elasticsearch offers several advantages that make it a popular choice for various applications, especially those requiring powerful search and analytics capabilities. Here are key advantages of Elasticsearch:

  1. Distributed and Scalable: Elasticsearch is built to be distributed, allowing for seamless scaling across multiple nodes. It can handle large volumes of data and traffic, making it suitable for high-performance and high-throughput applications.
  2. Real-Time Search: Elasticsearch provides real-time indexing, enabling users to search and retrieve data immediately after it is indexed. This makes it well-suited for applications that require real-time insights, such as log monitoring and analytics.
  3. Full-Text Search: Elasticsearch excels in full-text search, supporting advanced search functionalities, including fuzzy matching, wildcard searches, and proximity searches. This makes it a powerful tool for applications that rely on efficient and flexible search capabilities.
  4. Schema-Free: Elasticsearch is schema-less, allowing dynamic mapping of fields. This flexibility is advantageous for handling diverse and evolving data structures without the need for a predefined schema.
  5. Rich Query Language: Elasticsearch comes with a comprehensive Query DSL (Domain-Specific Language) that enables users to construct complex queries. This allows for precise and tailored searches, including filtering, aggregation, and sorting.
  6. Multi-Tenancy Support: Elasticsearch supports multi-tenancy, allowing multiple users or applications to use the same cluster while keeping their data isolated. This is valuable in environments where various teams or applications share resources.
  7. Open-Source and Active Community: Elasticsearch is open-source, meaning it is freely available for use, modification, and distribution. It has a vibrant and active community that contributes to its development, providing support, documentation, and a wealth of plugins.
  8. Text Analysis and Tokenization: Elasticsearch includes built-in text analysis and tokenization capabilities. This makes it suitable for natural language processing, linguistic analysis, and handling unstructured text data effectively.
  9. Ecosystem Integration (Elastic Stack): Elasticsearch is a core component of the Elastic Stack, which includes Logstash for data collection and Kibana for data visualization. This seamless integration creates a robust end-to-end solution for data processing and analysis.
  10. Support for Geospatial Data: Elasticsearch supports geospatial data types and queries, making it valuable for applications that involve geographic information and mapping.
  11. High Availability and Fault Tolerance: Elasticsearch ensures high availability and fault tolerance by replicating shards across nodes. In the event of a node failure, replicas can be promoted to primary, ensuring continued data accessibility.
  12. Security Features: Elasticsearch provides features for securing clusters, including role-based access control, authentication, and encryption, ensuring data privacy and protection.

These advantages make Elasticsearch a versatile and powerful tool for applications ranging from log analytics and search engines to business intelligence and monitoring systems.

Top 30 ElasticSearch Interview Questions for Freshers

1. What is the Elastic Stack?

  • Answer: The Elastic Stack, formerly known as ELK Stack, is a powerful suite of open-source tools: Elasticsearch, Logstash, and Kibana. It is designed for searching, analyzing, and visualizing data in real-time.

2. Explain Elasticsearch.

  • Answer: Elasticsearch is a distributed, RESTful search engine built on top of Apache Lucene. It provides a scalable solution for indexing and searching various types of data.

3. What is the role of Logstash in the Elastic Stack?

  • Answer: Logstash is responsible for collecting, processing, and transforming data before sending it to Elasticsearch. It supports a wide range of input sources and output destinations.

4. Differentiate between Elasticsearch and Apache Lucene.

  • Answer: Elasticsearch is a distributed search engine built on Apache Lucene. Lucene is a Java-based search library providing indexing and search capabilities, while Elasticsearch extends this functionality in a distributed and scalable manner.

5. Explain the concept of sharding in Elasticsearch.

  • Answer: Sharding involves dividing an index into smaller, manageable pieces called shards. Each shard is a self-contained index, allowing Elasticsearch to distribute and parallelize data across nodes.

6. What is a Node in Elasticsearch?

  • Answer: A node is a single instance of Elasticsearch running on a machine. Nodes work together to form a cluster and share the data and workload.

7. How does Elasticsearch achieve high availability?

  • Answer: Elasticsearch achieves high availability through data replication. Each shard has one or more replicas, ensuring that data is available even if a node fails.

8. Explain the purpose of Kibana.

  • Answer: Kibana is a data visualization and exploration tool for Elasticsearch. It allows users to create interactive dashboards, analyze data trends, and generate meaningful visualizations.

9. What is an Elasticsearch index alias?

  • Answer: An index alias is a way to associate multiple indices with a single, logical index name. This allows for easier management and querying of related data.

10. Discuss the significance of Beats in the Elastic Stack.

  • Answer: Beats are lightweight data shippers that send data from various sources to Elasticsearch or Logstash. They simplify the process of collecting and forwarding data.

11. How does Elasticsearch handle schema-less data?

  • Answer: Elasticsearch is schema-less, meaning it can index and search data without the need for a predefined schema. It dynamically maps fields based on the data it receives.

12. Explain the term ‘Mapping’ in Elasticsearch.

  • Answer: Mapping defines how documents and their fields are stored and indexed. It includes specifications for data types, analyzing processes, and other characteristics.

13. What is the purpose of an Elasticsearch Query DSL?

  • Answer: Query DSL (Domain-Specific Language) is used to define queries in Elasticsearch. It provides a flexible and powerful syntax for expressing complex queries.

14. Differentiate between “term” and “match” queries in Elasticsearch.

  • Answer: The “term” query matches exact terms, while the “match” query performs full-text search, analyzing the input and searching for relevant terms.

15. How can you secure an Elasticsearch cluster?

  •  Answer: Security measures include configuring authentication, encryption, role-based access control, and integrating with external authentication systems.

16. Explain the concept of an Elasticsearch Snapshot.

  • Answer: An Elasticsearch snapshot is a backup of a cluster’s indices and state. It allows for data recovery and migration.

17. Discuss the significance of the ‘bulk’ API in Elasticsearch.

  • Answer: The ‘bulk’ API enables efficient indexing or updating of multiple documents in a single request, reducing overhead and improving performance.

18. What is the purpose of the ‘cat’ API in Elasticsearch?

  • Answer: The ‘cat’ API provides a simplified view of cluster information, including indices, nodes, and more, in a human-readable format.

19. How does Elasticsearch handle conflicts during indexing?

  •  Answer: Elasticsearch uses optimistic concurrency control. If a conflict occurs during indexing, the document with the higher version number is considered the latest.

20. Explain the role of the ‘refresh’ API in Elasticsearch.

  • Answer: The ‘refresh’ API makes changes visible to search queries immediately. It is useful in scenarios where real-time search results are crucial.

21. Discuss the benefits of using Elasticsearch in a microservices architecture.

  • Answer: Elasticsearch facilitates efficient log management, real-time analytics, and centralized search functionalities, making it well-suited for microservices environments.

22. What is the purpose of the ‘nested’ datatype in Elasticsearch?

  • Answer: The ‘nested’ datatype allows the indexing of arrays or multiple objects within a single document, maintaining the relationships between them.

23. Explain the significance of the ‘fielddata’ parameter in Elasticsearch.

  • Answer: The ‘fielddata’ parameter determines whether a field can be loaded into memory for fast access during aggregations and sorting.

24. How does Elasticsearch handle geospatial data?

  • Answer: Elasticsearch supports geospatial data through the ‘geo_point’ datatype, enabling the indexing and searching of geographic coordinates.

25. Discuss the purpose of the ‘percolate’ query in Elasticsearch.

  • Answer: The ‘percolate’ query allows users to register queries and then check if a document matches any of those pre-registered queries.

26. Explain the role of the ‘cross_fields’ query type in Elasticsearch.

  • Answer: The ‘cross_fields’ query type is used in multi-field searches, analyzing each field independently and combining the results.

27. How can you improve the performance of an Elasticsearch cluster?

  • Answer: Performance optimization strategies include proper shard allocation, hardware scaling, query optimization, and regular monitoring.

28. Discuss the concept of ‘cluster coordination’ in Elasticsearch.

  • Answer: Cluster coordination involves communication between nodes to maintain a consistent cluster state, ensuring proper operation and data consistency.

29. What is the purpose of the ‘minimum_should_match’ parameter in Elasticsearch?

  •  Answer: The ‘minimum_should_match’ parameter defines the minimum number of ‘should’ clauses that must match for a query to be considered successful.

30. How does Elasticsearch handle index recovery after a node failure?

  • Answer: Elasticsearch ensures index recovery by replicating shards across nodes. In the event of a node failure, replicas are promoted to primary, ensuring continued availability.

External Resource

Elasticsearch Documentation


Mastering these top 30 Elastic interview questions provides a solid foundation for tackling interviews and showcasing your expertise in Elasticsearch and the Elastic Stack. Keep honing your skills, stay updated with the latest features, and approach interviews with confidence in your Elastic knowledge. Good luck!