Horizontal scaling mental model in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the shard key for horizontal scaling in MongoDB.

MongoDB

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

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

AuserId

Bdatabase

Ctimestamp

Dlocation

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a field that is not present in all documents

Using a field with low cardinality

The shard key determines how data is distributed across shards. Using userId is common for user-based data partitioning.

2fill in blank

medium

Complete the code to add a new shard to the MongoDB cluster.

MongoDB

sh.addShard("[1]")

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

Amongos:27017

Badmin:27017

Cconfigsvr:27019

Dshard0001/mongo1:27017

Attempts:

3 left

💡 Hint

Common Mistakes

Using mongos or config server address instead of shard address

The addShard command requires the shard's replica set name and host address, like shard0001/mongo1:27017.

3fill in blank

hard

Fix the error in the command to enable sharding on a database.

MongoDB

sh.enableSharding("[1]")

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

Aadmin

Bmydb

Cconfig

Dlocal

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to shard system databases like admin or config

Sharding is enabled on user databases like mydb. System databases like admin, config, and local cannot be sharded.

4fill in blank

hard

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

MongoDB

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

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

AcustomerId

BorderDate

Cstatus

Dregion

Attempts:

3 left

💡 Hint

Common Mistakes

Using unrelated fields that don't help distribute data evenly

A compound shard key with customerId and orderDate helps distribute data by user and time, improving balance and query efficiency.

5fill in blank

hard

Fill all three blanks to configure a MongoDB sharded cluster with a config server, shard, and mongos router.

MongoDB

config = new Mongo("[1]")
sh.addShard("[2]")
mongos = new Mongo("[3]")

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

Aconfigsvr1:27019

Bshard0002/mongo2:27017

Cmongos1:27017

Dadmin:27017

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up ports or using admin database address

The config server runs on configsvr1:27019, the shard is shard0002/mongo2:27017, and the mongos router is mongos1:27017.