Backup and restore strategies in MongoDB - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding MongoDB Backup Types

Which of the following backup types in MongoDB allows you to capture the database state at a specific point in time without stopping the database?

A Logical backup

B Cold backup

C Incremental backup

D Hot backup

💡 Hint

Think about backups that do not require shutting down the database.

A hot backup captures the database while it is running, allowing continuous operations without downtime.

❓ query_result

intermediate

Result of mongodump Command

What is the expected output when running the command mongodump --db mydb --out /backup/?

A A directory named 'mydb' inside '/backup/' containing BSON data files

B A single JSON file named 'mydb.json' inside '/backup/'

C A compressed archive file named 'mydb.archive' inside '/backup/'

D An error because --out requires a file name, not a directory

💡 Hint

Consider how mongodump organizes data when backing up a database.

mongodump creates a directory with the database name inside the specified output directory, containing BSON files for each collection.

📝 Syntax

advanced

Correct mongorestore Syntax

Which of the following commands correctly restores a MongoDB database from a backup directory named '/backup/mydb'?

A mongorestore --restore-db mydb /backup/mydb

B mongorestore /backup/mydb --db=mydb

C mongorestore --db mydb /backup/mydb

D mongorestore --database mydb /backup/mydb

💡 Hint

Check the official mongorestore syntax for specifying the database and source directory.

The correct syntax uses --db to specify the target database followed by the path to the backup directory.

❓ optimization

advanced

Optimizing Backup Speed

You want to speed up the backup process of a large MongoDB database using mongodump. Which option will help achieve this?

A Use --numParallelCollections to dump multiple collections at once

B Use --gzip to compress data during dump

C Use --oplog to include the oplog in the dump

D Use --query to dump only a subset of documents

💡 Hint

Think about parallelizing work to improve speed.

--numParallelCollections allows mongodump to dump multiple collections simultaneously, improving speed.

🔧 Debug

expert

Troubleshooting mongorestore Failure

You run mongorestore --db mydb /backup/mydb but get an error: Failed: error reading collection data. What is the most likely cause?

A The MongoDB server is not running

B The backup was created with --gzip but mongorestore is not using --gzip

C The mongorestore command is missing the --drop option

D The backup directory '/backup/mydb' does not contain BSON files

💡 Hint

Consider if the backup files are compressed and how mongorestore handles them.

If the backup was compressed with --gzip, mongorestore must also use --gzip to read the files correctly.