ElasticSearch ElasticSearch Core Concepts & Architecture 2

Question 1

What does 'inverted index' mean in Elasticsearch?

Accepted Answer

A data structure mapping terms to documents containing them

Answer

An inverted index maps each unique term to the list of documents in which it appears, enabling fast full-text search.

Question 2

What is the default number of primary shards when creating an index in Elasticsearch 7.x and later?

Accepted Answer

1

Answer

Starting from Elasticsearch 7.0, the default number of primary shards per index was changed from 5 to 1.

Question 3

What is a 'mapping' in Elasticsearch?

Accepted Answer

The schema definition for documents in an index

Answer

A mapping defines how documents and their fields are stored and indexed, similar to a schema in a relational database.

Question 4

What does the 'near real-time' (NRT) property of Elasticsearch mean?

Accepted Answer

Data is available for search within about 1 second after indexing

Answer

Near real-time means there is a slight latency (usually around 1 second) between indexing a document and it becoming searchable.

Question 5

What is the purpose of the Elasticsearch '_id' field?

Accepted Answer

It uniquely identifies each document within an index

Answer

The '_id' field is a unique identifier for each document within an index and is used to retrieve, update, or delete specific documents.

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