Shard key selection importance in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the shard key when sharding a collection.

MongoDB

sh.shardCollection("mydb.users", [1])

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

A"userId"

B{ userId: 1 }

C{ age: 1 }

D{ location: 1 }

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string instead of a document for the shard key.

Choosing a field that is not suitable as a shard key.

The shard key must be specified as a document indicating the field(s) to shard on. Here, { userId: 1 } is the correct shard key.

2fill in blank

medium

Complete the code to create an index on the shard key field.

MongoDB

db.users.createIndex({ [1]: 1 })

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

Aage

Blocation

Cemail

DuserId

Attempts:

3 left

💡 Hint

Common Mistakes

Creating an index on a non-shard key field.

Forgetting to create an index on the shard key.

The shard key field must be indexed for efficient query routing. Here, userId is the shard key field.

3fill in blank

hard

Fix the error in the shard key selection to avoid unbalanced data distribution.

MongoDB

sh.shardCollection("mydb.orders", { [1]: 1 })

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

AcustomerId

BorderDate

Cstatus

DtotalAmount

Attempts:

3 left

💡 Hint

Common Mistakes

Using a field with few distinct values as shard key.

Choosing a field not used in queries.

Choosing customerId as the shard key helps distribute data evenly because it has high cardinality and is frequently used in queries.

4fill in blank

hard

Fill both blanks to create a compound shard key for better data distribution.

MongoDB

sh.shardCollection("mydb.logs", { [1]: 1, [2]: 1 })

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

AuserId

Btimestamp

Cregion

Dstatus

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing fields that do not improve data distribution.

Using only one field when a compound key is better.

A compound shard key with timestamp and region helps distribute data by time and location, improving balance and query performance.

5fill in blank

hard

Fill all three blanks to define a shard key and create an index for efficient queries.

MongoDB

sh.shardCollection("mydb.sales", { [1]: 1, [2]: 1 });
db.sales.createIndex({ [3]: 1 })

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

Aregion

BproductId

DsaleDate

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same field for all blanks.

Not creating an index on a frequently queried field.

The shard key is a compound key on region and productId. The index on saleDate helps queries filter by date efficiently.