Which of the following MongoDB concepts is MOST closely related to the 'A' in ACID properties within the context of transactions?
Atomicity
Authorization
Authentication
Aggregation
Which component in a sharded cluster is responsible for routing read and write operations to the appropriate shards?
Mongos router
Replica set
Shard server
Config server
What is a key difference between single-document writes and multi-document transactions in MongoDB?
Multi-document transactions can only update a single document at a time.
Single-document writes offer ACID guarantees, while multi-document transactions do not.
Multi-document transactions provide atomicity across multiple documents, while single-document writes do not.
Single-document writes are only supported in sharded clusters, while multi-document transactions work in both standalone and sharded environments.
How does creating indexes on appropriate fields impact the performance of aggregation queries in MongoDB?
Indexes can significantly improve aggregation performance
Indexes are only relevant for find() queries, not aggregation
Indexes have no impact on aggregation performance
Indexes can negatively affect aggregation performance
How can you improve the performance of a $lookup operation in MongoDB?
Use $sort after the $lookup stage
Avoid using $lookup altogether
Use $project to limit fields returned after the $lookup
Use $match to filter documents before the $lookup stage
What happens during a failover event in a MongoDB replica set?
The primary node automatically recovers.
A new primary node is elected from the available secondaries.
All read and write operations are halted indefinitely.
Data is automatically restored from backups.
What is the purpose of the $lookup stage in the MongoDB aggregation pipeline?
Updating documents
Joining documents from different collections
Filtering documents
Sorting documents
Which of these is a benefit of reading from secondary nodes in a MongoDB replica set?
Lower storage costs
Faster write operations
Increased data security
Reduced load on the primary node
What is a shard key in MongoDB's sharding system?
A unique identifier assigned to each shard server
A field or set of fields used to distribute data across shards
An encryption key used for securing data on shards
A password used to authenticate connections to the cluster
Which stage of the MongoDB write path is responsible for applying write operations to the journal?
Write to Journal
Apply Operation
Intent Shared Lock
Release Locks