ElasticSearch Cheat Sheet 2026

The 30 highest-yield ElasticSearch facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. What happens when cluster.routing.allocation.enable is set to 'none' in Elasticsearch? → All shard allocations are disabled, preventing any new shard assignments
2. An Index may be divided into several → Shards
3. Which API is used to check the health of an Elasticsearch cluster? → GET /_cluster/health
4. What does the 'update by query' API do in Elasticsearch? → Updates all documents that match a query using a script or partial update
5. What is the 'explain' API in Elasticsearch used for? → Showing how a relevance score was calculated for a specific document
6. What is the default number of primary shards per index in Elasticsearch 7.x and later? → 1
7. Why is documentation important in ElasticSearch risk management? → It creates an audit trail, supports decision-making, and demonstrates due diligence
8. The replica shard is a copy of the original shard. → Primary
9. What does the Elasticsearch 'highlight' feature do? → Returns snippets of matched text with search terms highlighted
10. The default communication port for Elasticsearch is → 9300/tcp
11. What does the 'size' parameter control in an Elasticsearch search request? → The maximum number of hits returned in the response
12. Which approach best demonstrates professional competency in ElasticSearch practice? → Integrating continuing education, practical experience, and evidence-based decision making
13. What is a 'multi_match' query in Elasticsearch? → A query that runs the same match query across multiple fields
14. What is the primary value of case study analysis in ElasticSearch training? → Developing critical thinking by applying theory to realistic professional scenarios
15. How should an ElasticSearch professional handle a situation outside their scope of competency? → Recognize limitations and refer to or consult with appropriate specialists
16. Which Elasticsearch API provides a detailed explanation of why a specific shard is unassigned or in its current allocation state? → GET /_cluster/allocation/explain
17. How should an ElasticSearch professional respond to a compliance violation? → Report it promptly, investigate the root cause, and implement corrective actions
18. What is a 'bool' query in Elasticsearch used for? → Combining multiple query clauses using must, should, must_not, and filter
19. What is the bare minimum of master nodes that a cluster must have? → three
20. What is the Query DSL in Elasticsearch? → A JSON-based language for defining queries
21. What does a 'terms' aggregation return in Elasticsearch? → The top unique values of a field with their document counts
22. How has digital technology transformed ElasticSearch practice? → It has enhanced data collection, analysis, communication, and operational efficiency
23. Coding language employed by Elasticsearch → Java
24. What is the purpose of the Elasticsearch '_id' field? → It uniquely identifies each document within an index
25. What is the purpose of the 'shrink' API in Elasticsearch? → Reducing the number of primary shards in an index
26. Why is evidence-based practice important in ElasticSearch? → It integrates best available evidence with professional expertise for optimal outcomes
27. What is the benefit of interdisciplinary collaboration in ElasticSearch practice? → It brings diverse expertise and perspectives that improve outcomes and innovation
28. What is a 'range' query in Elasticsearch? → A query that finds documents where a field value falls within a specified range
29. How do ElasticSearch professionals establish measurable quality objectives? → By defining specific, measurable, achievable, relevant, and time-bound quality targets
30. An Elasticsearch cluster may have a variety of nodes, including the following: → Master, Data, Coordinating