MongoDB Quiz ( Intermediate ) - All Questions

This intermediate-level MongoDB quiz is designed for developers who understand the basics and want to test applied, real-world MongoDB concepts. It focuses on querying, indexing, aggregation, schema design, performance, and common interview scenarios.

Question 1: What is the main purpose of MongoDB indexes?

Reduce storage size
Improve query performance
Enforce schema rules
Handle replication

Explanation: Indexes speed up query execution by reducing scanned documents.

Question 2: Which index type supports range-based queries efficiently?

Hashed index
Text index
Single-field index
Wildcard index

Explanation: Single-field indexes efficiently support range queries.

Question 3: What does a compound index do?

Indexes multiple fields together
Indexes arrays only
Indexes nested documents
Indexes text content

Explanation: Compound indexes include multiple fields in a defined order.

Question 4: Which MongoDB command analyzes query performance?

analyze()
explain()
profile()
debug()

Explanation: explain() shows how MongoDB executes a query.

Question 5: What does the aggregation framework primarily provide?

CRUD operations
Schema validation
Data processing and transformation
User authentication

Explanation: Aggregation processes and transforms data through stages.

Question 6: Which aggregation stage filters documents?

$project
$group
$match
$sort

Explanation: $match filters documents in the pipeline.

Question 7: Which aggregation stage reshapes documents?

$group
$project
$match
$limit

Explanation: $project controls fields and structure.

Question 8: Which aggregation stage groups documents?

$group
$sort
$count
$lookup

Explanation: $group groups documents by a key.

Question 9: Which operator calculates the total of numeric values?

$avg
$sum
$count
$total

Explanation: $sum adds numeric values.

Question 10: Which operator calculates an average value?

$mean
$avg
$sum
$median

Explanation: $avg computes the average.

Question 11: What is the default index created on every collection?

id
_id
primary
auto

Explanation: MongoDB automatically creates an index on _id.

Question 12: Which index is best for text search?

Hashed index
Text index
Wildcard index
Geospatial index

Explanation: Text indexes support text search queries.

Question 13: Which operator performs a join-like operation?

$merge
$lookup
$union
$connect

Explanation: $lookup performs left outer joins.

Question 14: What does schema validation enforce?

Index structure
Document shape and rules
Replication behavior
Query limits

Explanation: Schema validation enforces document structure.

Question 15: Which command enables schema validation?

createCollection()
validateSchema()
db.validate()
enforceSchema()

Explanation: Schema rules are defined during createCollection.

Question 16: Which write concern ensures data is written to disk?

w:0
j:true
w:1
majority

Explanation: j:true ensures journal commit.

Question 17: What does read preference control?

Which index is used
Which replica set member is read from
Query execution time
Aggregation behavior

Explanation: Read preference controls read source.

Question 18: Which read preference ensures strongest consistency?

secondary
nearest
primary
secondaryPreferred

Explanation: Primary ensures up-to-date reads.

Question 19: What is a replica set?

A backup snapshot
A group of MongoDB servers
A sharded cluster
An index group

Explanation: Replica sets provide redundancy and availability.

Question 20: Which node accepts write operations in a replica set?

Secondary
Arbiter
Primary
Hidden

Explanation: Writes go to the primary node.

Question 21: What is the purpose of an arbiter?

Store data
Resolve elections
Handle queries
Cache writes

Explanation: Arbiters help in primary elections.

Question 22: What does sharding primarily solve?

High availability
Horizontal scaling
Schema enforcement
Indexing speed

Explanation: Sharding distributes data across servers.

Question 23: What is a shard key?

Primary key
Index key
Partitioning field
Foreign key

Explanation: Shard key determines data distribution.

Question 24: Which shard key property is most important?

Low cardinality
High write frequency
Even data distribution
Small data size

Explanation: Even distribution avoids hotspots.

Question 25: Which operator limits aggregation results?

$skip
$limit
$cap
$slice

Explanation: $limit restricts result count.

Question 26: Which operator skips documents in aggregation?

$offset
$jump
$skip
$ignore

Explanation: $skip skips a number of documents.

Question 27: Which stage sorts aggregation results?

$group
$order
$sort
$rank

Explanation: $sort orders documents.

Question 28: What does $unwind do?

Merges arrays
Splits array elements into documents
Removes arrays
Indexes arrays

Explanation: $unwind deconstructs arrays.

Question 29: Which index type supports geospatial queries?

Text
2dsphere
Hashed
Wildcard

Explanation: 2dsphere supports location-based queries.

Question 30: Which method replaces an entire document?

updateOne()
replaceOne()
updateMany()
modify()

Explanation: replaceOne replaces the whole document.

Question 31: Which update operator removes a field?

$unset
$delete
$remove
$pop

Explanation: $unset removes a field.

Question 32: Which operator removes an element from an array?

$pull
$unset
$pop
$slice

Explanation: $pull removes matching array elements.

Question 33: Which operator adds unique values to an array?

$push
$addToSet
$insert
$append

Explanation: $addToSet avoids duplicates.

Question 34: Which feature prevents duplicate documents?

Replication
Unique index
Schema validation
Shard key

Explanation: Unique indexes enforce uniqueness.

Question 35: What does TTL index do?

Encrypt data
Auto-delete documents
Optimize reads
Limit writes

Explanation: TTL indexes remove expired documents.

Question 36: Which command shows collection statistics?

db.stats()
collStats()
collection.info()
db.collection.stats()

Explanation: stats() shows collection metrics.

Question 37: Which metric indicates index usage?

Docs examined
Execution time
Index hits
Keys examined

Explanation: Keys examined shows index usage.

Question 38: What does covered query mean?

Uses multiple indexes
Uses only index without reading documents
Scans all documents
Uses aggregation

Explanation: Covered queries read only indexes.

Question 39: Which isolation level does MongoDB provide?

Serializable
Snapshot isolation
Read committed
Repeatable read

Explanation: MongoDB provides snapshot isolation.

Question 40: Which feature ensures atomic updates on a document?

Indexes
Transactions
Document-level atomicity
Replication

Explanation: Single document updates are atomic.

Question 41: Which version introduced multi-document transactions?

Explanation: MongoDB 4.0 introduced transactions.

Question 42: Which transaction property ensures durability?

Consistency
Isolation
Durability
Availability

Explanation: Durability ensures data persistence.

Question 43: Which backup method allows point-in-time recovery?

mongodump
Filesystem copy
Oplog backup
Snapshot only

Explanation: Oplog backups support point-in-time recovery.

Question 44: Which tool is commonly used for MongoDB backups?

mongoexport
mongodump
mongostat
mongotop

Explanation: mongodump is used for backups.

Question 45: Which tool monitors real-time performance?

mongostat
mongoimport
mongodump
mongorestore

Explanation: mongostat shows real-time stats.

Question 46: Which schema design suits one-to-many relationships best?

Referencing
Embedding
Normalization
Sharding

Explanation: Embedding works well for one-to-many.

Question 47: What is the biggest risk of excessive embedding?

Slow reads
Document size limit
Index overhead
Query complexity

Explanation: Documents are limited to 16MB.

Question 48: Which design improves write-heavy workloads?

Heavy indexing
Minimal indexes
Complex aggregation
Joins

Explanation: Fewer indexes improve write performance.

Question 49: What is the main goal of MongoDB at scale?

Strict schemas
Horizontal scalability
Complex joins
Strong normalization

Explanation: MongoDB is designed for horizontal scaling.

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MongoDB Quiz ( Intermediate )

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