Index settings (shards, replicas) in Elasticsearch - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the default number of primary shards for a new Elasticsearch index?

By default, when you create a new index in Elasticsearch without specifying shard settings, how many primary shards does it have?

A 5

B 0

C 3

D 1

💡 Hint

Think about the default shard count Elasticsearch uses for balancing data.

Elasticsearch creates 5 primary shards by default for each new index unless specified otherwise.

❓ query_result

intermediate

How many replicas are created by default for an Elasticsearch index?

When you create an index in Elasticsearch without specifying replica settings, how many replica shards are created by default?

A 0

B 1

C 2

D 5

💡 Hint

Replicas provide fault tolerance and improve search performance.

By default, Elasticsearch creates 1 replica shard for each primary shard.

📝 Syntax

advanced

Which JSON snippet correctly sets an index with 3 primary shards and 2 replicas?

Select the valid JSON configuration to create an Elasticsearch index with 3 primary shards and 2 replicas.

A { "settings": { "number_of_shards": 3, "number_of_replicas": 2 } }

B { "settings": { "shards": 3, "replicas": 2 } }

C { "settings": { "number_of_shards": "3", "number_of_replicas": "2" } }

D { "settings": { "primary_shards": 3, "replica_shards": 2 } }

💡 Hint

Look for the exact keys Elasticsearch expects for shard settings.

Elasticsearch expects the keys 'number_of_shards' and 'number_of_replicas' with integer values.

🧠 Conceptual

advanced

Why should you avoid setting the number of primary shards too high for a small index?

What is the main reason to avoid configuring too many primary shards for a small Elasticsearch index?

A It automatically disables replicas for the index.

B It causes Elasticsearch to reject writes to the index.

C It merges all shards into one, reducing parallelism.

D It increases cluster overhead and wastes resources without improving performance.

💡 Hint

Think about resource use and efficiency.

Too many shards for small data cause unnecessary resource use and slow cluster operations.

🔧 Debug

expert

What error occurs if you try to set number_of_shards to 0 when creating an index?

You run this command to create an index with zero primary shards: { "settings": { "number_of_shards": 0, "number_of_replicas": 1 } } What error will Elasticsearch return?

A No error, index created with zero shards

B IndexCreationException: replicas cannot be set without shards

C ValidationException: number_of_shards must be greater than 0

D ClusterBlockException: cluster is blocked due to invalid shard count

💡 Hint

Primary shards must be at least one for an index to exist.

Elasticsearch requires at least one primary shard; zero is invalid and triggers a validation error.