MongoDB installation and setup - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding MongoDB default port

What is the default port number MongoDB server listens on after installation?

A 27017

B 3306

C 8080

D 5432

💡 Hint

Think about the standard port MongoDB uses, different from MySQL or PostgreSQL.

MongoDB by default listens on port 27017. Ports 3306 and 5432 are for MySQL and PostgreSQL respectively, and 8080 is commonly used for web servers.

❓ query_result

intermediate

Check MongoDB service status command output

After installing MongoDB on a Linux system, you run systemctl status mongod. What output indicates the service is running correctly?

A Active: inactive (dead)

B Active: active (running) since ...

C Failed to start mongod.service: Unit not found.

D Active: activating (start) since ...

💡 Hint

Look for the word that means the service is currently working.

The status line showing active (running) means MongoDB is running properly. Other statuses indicate stopped, failed, or starting states.

📝 Syntax

advanced

Correct command to start MongoDB manually

Which of the following commands correctly starts the MongoDB server manually on a Linux system?

A sudo systemctl start mongod

B sudo mongod --start

C mongod start

D service mongod run

💡 Hint

Use the standard Linux service manager command.

The correct way to start MongoDB service is using systemctl start mongod. Other commands are either invalid or incorrect syntax.

🔧 Debug

advanced

Troubleshooting MongoDB connection error

You installed MongoDB and started the service, but when running mongo shell, you get Failed to connect to 127.0.0.1:27017. What is the most likely cause?

A MongoDB is listening on port 3306

B Firewall is blocking port 5432

C Mongo shell command is misspelled

D MongoDB service is not running

💡 Hint

Check if the server process is active before connecting.

If the MongoDB service is not running, the shell cannot connect to the default port 27017. Ports 3306 and 5432 are unrelated, and the shell command is correct.

❓ optimization

expert

Optimizing MongoDB startup for production

Which startup option improves MongoDB performance by enabling journaling and limiting memory usage?

A mongod --journal --cacheSize 8GB

B mongod --nojournal --cacheSize 4GB

C mongod --journal --wiredTigerCacheSizeGB 2

D mongod --nojournal --wiredTigerCacheSizeGB 1

💡 Hint

Journaling helps data safety; cache size controls memory use.

Option C enables journaling for data durability and sets WiredTiger cache size to 2GB, balancing performance and memory. Other options disable journaling or use invalid flags.