Index settings (shards, replicas) in Elasticsearch - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the number of primary shards to 3.

Elasticsearch

{
  "settings": {
    "number_of_shards": [1]
  }
}

Drag options to blanks, or click blank then click option'

A5

B0

C1

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Setting shards to 0 is invalid because an index must have at least one shard.

Choosing too many shards can cause overhead.

The number_of_shards setting controls how many primary shards the index has. Setting it to 3 means the index will be split into 3 parts.

2fill in blank

medium

Complete the code to set the number of replicas to 2.

Elasticsearch

{
  "settings": {
    "number_of_replicas": [1]
  }
}

Drag options to blanks, or click blank then click option'

A1

B2

C-1

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Negative numbers are invalid for replicas.

Setting replicas too high wastes resources.

The number_of_replicas setting controls how many copies of each shard are kept for fault tolerance. Setting it to 2 means there will be two copies of each shard.

3fill in blank

hard

Fix the error in the code to correctly set shards to 1.

Elasticsearch

{
  "settings": {
    "number_of_shards": [1]
  }
}

Drag options to blanks, or click blank then click option'

A1

Bone

Ctrue

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string like "one" instead of a number.

Using boolean or null values.

The number_of_shards must be a number, not a string or other type. Using 1 as a number is correct.

4fill in blank

hard

Fill both blanks to set shards to 4 and replicas to 1.

Elasticsearch

{
  "settings": {
    "number_of_shards": [1],
    "number_of_replicas": [2]
  }
}

Drag options to blanks, or click blank then click option'

A4

B1

C3

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up shards and replicas values.

Using zero for shards which is invalid.

Setting number_of_shards to 4 splits the index into 4 parts. Setting number_of_replicas to 1 keeps one copy of each shard for safety.

5fill in blank

hard

Fill all three blanks to set shards to 2, replicas to 0, and refresh interval to 1s.

Elasticsearch

{
  "settings": {
    "number_of_shards": [1],
    "number_of_replicas": [2],
    "refresh_interval": "[3]"
  }
}

Drag options to blanks, or click blank then click option'

A1

B0

C2

D1s

Attempts:

3 left

💡 Hint

Common Mistakes

Putting numbers in quotes for shards or replicas.

Using invalid refresh interval formats.

Setting number_of_shards to 2 splits the index into two parts. Setting number_of_replicas to 0 means no copies. The refresh_interval of "1s" means the index refreshes every second.

Practice

1. What is the main purpose of setting number_of_shards in an Elasticsearch index?

easy

A. To define the size of the index

B. To create backup copies of data

C. To split data into parts for faster searching

D. To set the maximum number of documents

Solution

1. Step 1: Understand shards role

   Shards divide the index data into smaller parts to allow parallel searching.

2. Step 2: Differentiate shards from replicas

   Replicas are copies for safety, not for splitting data.

3. Final Answer:

   To split data into parts for faster searching -> Option C

4. Quick Check:

   Shards = split data for speed [OK]

Hint: Shards split data, replicas copy data [OK]

Common Mistakes:

• Confusing shards with replicas
• Thinking shards create backups
• Assuming shards set index size

2. Which of the following is the correct way to set 3 shards and 2 replicas in an Elasticsearch index creation JSON?

easy

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

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

C. { "settings": { "shard_count": 3, "replica_count": 2 } }

D. { "settings": { "num_shards": 3, "num_replicas": 2 } }

Solution

1. Step 1: Recall correct setting keys

   The official keys are number_of_shards and number_of_replicas.

2. Step 2: Match keys with options

   Only { "settings": { "number_of_shards": 3, "number_of_replicas": 2 } } uses the exact correct keys and valid JSON format.

3. Final Answer:

   { "settings": { "number_of_shards": 3, "number_of_replicas": 2 } } -> Option A

4. Quick Check:

   Correct keys = number_of_shards, number_of_replicas [OK]

Hint: Use full keys: number_of_shards and number_of_replicas [OK]

Common Mistakes:

• Using shorthand keys like shards or replicas
• Wrong JSON syntax
• Mixing shard and replica counts

3. Given an index with number_of_shards set to 4 and number_of_replicas set to 1, how many total shard copies exist in the cluster?

medium

A. 4

B. 6

C. 5

D. 8

Solution

1. Step 1: Calculate primary shards

   There are 4 primary shards as set.

2. Step 2: Calculate replica shards

   Each primary shard has 1 replica, so 4 replicas total.

3. Step 3: Add primary and replicas

   Total shards = 4 primary + 4 replicas = 8 shards.

4. Final Answer:

   8 -> Option D

5. Quick Check:

   Total shards = primary + replicas = 8 [OK]

Hint: Total shards = shards x (1 + replicas) [OK]

Common Mistakes:

• Counting only primary shards
• Adding shards and replicas incorrectly
• Confusing replicas with shards

4. You tried to create an index with this setting: { "settings": { "number_of_shards": 2, "number_of_replicas": -1 } }. What is the problem?

medium

A. Negative replicas value is invalid

B. Number of shards cannot be 2

C. Missing required field for replicas

D. JSON syntax error

Solution

1. Step 1: Check shards value

   Number of shards is 2, which is valid.

2. Step 2: Check replicas value

   Replicas cannot be negative; -1 is invalid.

3. Final Answer:

   Negative replicas value is invalid -> Option A

4. Quick Check:

   Replicas must be zero or positive [OK]

Hint: Replicas cannot be negative numbers [OK]

Common Mistakes:

• Assuming negative replicas mean no replicas
• Thinking shards must be > 3
• Ignoring JSON correctness

5. You want to create an index optimized for high availability with 5 shards. Which setting combination is best to ensure data safety and fast search?

hard

A. { "number_of_shards": 5, "number_of_replicas": 0 }

B. { "number_of_shards": 5, "number_of_replicas": 1 }

C. { "number_of_shards": 1, "number_of_replicas": 5 }

D. { "number_of_shards": 10, "number_of_replicas": 1 }

Solution

1. Step 1: Understand shards and replicas roles

   Shards split data for speed; replicas provide copies for safety.

2. Step 2: Evaluate options for availability and speed

   { "number_of_shards": 5, "number_of_replicas": 1 } keeps 5 shards for speed and 1 replica for safety, balancing both.

3. Step 3: Reject other options

   The option with zero replicas has no safety, the option with 1 shard is slow for search, the option with 10 shards has overhead.

4. Final Answer:

   { "number_of_shards": 5, "number_of_replicas": 1 } -> Option B

5. Quick Check:

   Balance shards and replicas for speed and safety [OK]

Hint: Balance shards for speed and replicas for safety [OK]

Common Mistakes:

• Setting zero replicas for safety
• Using too few shards for speed
• Over-sharding causing overhead