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Apache Cassandra MCQs
Here, we have provided the top Apache Cassandra multiple-choice questions and answers with explanations. You can go through these questions to learn and enhance your skills in Apache Cassandra. These questions are also helpful for preparing for exams like the Apache Cassandra certification courses and other related professional certifications.
List of Apache Cassandra MCQs
Here is a list of the top 50 Apache Cassandra multiple-choice questions and answers, along with explanations:
1. What type of database is Cassandra?
- Relational Database
- NoSQL Database
- Hierarchical Database
- Graph Database
Answer: B) NoSQL Database
Explanation:
Cassandra is a distributed NoSQL database designed for handling large amounts of data across multiple servers with high availability.
2. What is a key advantage of Cassandra?
- Supports only vertical scaling
- Has a single point of failure
- Provides high availability and fault tolerance
- Works only on Windows OS
Answer: C) Provides high availability and fault tolerance
Explanation:
Cassandra is built to be highly available and fault-tolerant, with no single point of failure due to its distributed architecture.
3. In Cassandra, what is a Keyspace?
- A table containing user data
- The highest level of data organization
- A type of query language
- A method to delete data
Answer: B) The highest level of data organization
Explanation:
A keyspace in Cassandra is the top-level namespace that contains tables and defines replication settings for the data stored within it.
4. Which command is used to open the Cassandra Query Language Shell (CQLSH)?
- start_cassandra
- cassandra --shell
- cqlsh
- open_cql
Answer: C) cqlsh
Explanation:
The "cqlsh" command launches the Cassandra Query Language Shell, which allows users to interact with the database using CQL commands.
5. What does the replication factor define in Cassandra?
- The number of queries executed per second
- The number of times data is copied across nodes
- The amount of RAM required
- The number of CPU cores used
Answer: B) The number of times data is copied across nodes
Explanation:
Replication factor determines how many copies of data exist across the cluster to ensure high availability and fault tolerance.
6. What is the primary query language used in Cassandra?
- SQL
- HQL
- CQL
- JSON
Answer: C) CQL
Explanation:
Cassandra Query Language (CQL) is used to interact with Cassandra databases, similar to SQL but optimized for NoSQL operations.
7. Which component of Cassandra ensures data durability?
- Memtable
- Commit Log
- SSTable
- Cache
Answer: B) Commit Log
Explanation:
The commit log records all write operations and ensures durability in case of system failure before data is written to disk.
8. What is a node in Cassandra?
- A row in a table
- A column in a table
- An individual machine in a cluster
- A special type of query
Answer: C) An individual machine in a cluster
Explanation:
A node in Cassandra is a single machine within a distributed cluster, responsible for storing and managing data.
9. What is the purpose of a partition key in Cassandra?
- To uniquely identify rows in a table
- To define the structure of a table
- To distribute data evenly across nodes
- To execute queries faster
Answer: C) To distribute data evenly across nodes
Explanation:
The partition key determines how data is distributed across the cluster by assigning records to specific nodes.
10. What does the term "eventual consistency" mean in Cassandra?
- Data is always consistent across all nodes
- Data updates are immediately reflected across all nodes
- Data might not be instantly consistent but will become consistent over time
- Data consistency is not maintained at all
Answer: C) Data might not be instantly consistent but will become consistent over time
Explanation:
Eventual consistency means that while updates may not be immediately visible on all nodes, the system will eventually sync to reflect accurate data.
11. What type of architecture does Cassandra use?
- Master-Slave
- Client-Server
- Peer-to-Peer
- Hierarchical
Answer: C) Peer-to-Peer
Explanation:
Cassandra follows a peer-to-peer architecture where all nodes are equal, eliminating the risk of a single point of failure.
12. Which of the following is NOT a feature of Cassandra?
- Horizontal scalability
- Strong consistency by default
- Fault tolerance
- High availability
Answer: B) Strong consistency by default
Explanation:
Cassandra prioritizes availability and partition tolerance over strong consistency, following the CAP theorem.
13. What is the role of a super column in Cassandra?
- It is a column that acts as a primary key
- It is a collection of columns within a row
- It is used for indexing tables
- It is used for transaction control
Answer: B) It is a collection of columns within a row
Explanation:
A super column is a container for multiple related columns, helping to structure complex hierarchical data in Cassandra.
14. What command is used to create a keyspace in Cassandra?
- CREATE DATABASE
- CREATE TABLE
- CREATE KEYSPACE
- USE KEYSPACE
Answer: C) CREATE KEYSPACE
Explanation:
The "CREATE KEYSPACE" command is used to define a new keyspace and configure its replication strategy.
15. How does Cassandra handle failed nodes?
- It stops the entire cluster
- It automatically reroutes queries to other nodes
- It requires manual restart of the cluster
- It deletes data stored on the failed node
Answer: B) It automatically reroutes queries to other nodes
Explanation:
Since Cassandra is a fault-tolerant system, if a node fails, requests are automatically rerouted to other available nodes.
16. Which of the following is a valid data model in Cassandra?
- Document-based model
- Column-family model
- Key-value model
- Graph model
Answer: B) Column-family model
Explanation:
Cassandra uses a column-family data model, where data is stored in tables consisting of rows and columns, optimized for distributed storage.
17. What is the role of the Gossip Protocol in Cassandra?
- Ensures data encryption
- Manages node-to-node communication
- Handles query execution
- Creates backups automatically
Answer: B) Manages node-to-node communication
Explanation:
The Gossip Protocol allows Cassandra nodes to exchange state information and maintain cluster health.
18. What is the primary purpose of compaction in Cassandra?
- Deletes old data permanently
- Optimizes data storage by merging SSTables
- Encrypts sensitive data
- Speeds up read queries
Answer: B) Optimizes data storage by merging SSTables
Explanation:
Compaction in Cassandra merges SSTables to reduce storage overhead, remove tombstones, and improve read performance.
19. What is a tombstone in Cassandra?
- A deleted data marker
- A corrupted data record
- A log entry for backup
- A new type of keyspace
Answer: A) A deleted data marker
Explanation:
A tombstone is a marker placed on deleted data in Cassandra, indicating that the data should be removed during compaction.
20. Which of the following best describes the CAP theorem in the context of Cassandra?
- Cassandra provides strong consistency at all times
- Cassandra prioritizes availability and partition tolerance over consistency
- Cassandra does not support partition tolerance
- Cassandra strictly follows ACID principles
Answer: B) Cassandra prioritizes availability and partition tolerance over consistency
Explanation:
According to the CAP theorem, Cassandra favors high availability and partition tolerance, achieving eventual consistency.
21. Which replication strategy is best suited for a multi-data-center Cassandra deployment?
- SimpleStrategy
- NetworkTopologyStrategy
- LocalStrategy
- ReplicationFactorStrategy
Answer: B) NetworkTopologyStrategy
Explanation:
NetworkTopologyStrategy allows replication across multiple data centers, optimizing data availability and fault tolerance.
22. In Cassandra, what does "snitch" determine?
- Which nodes should store a given piece of data
- The query execution plan
- The schema design of a table
- The data type of columns
Answer: A) Which nodes should store a given piece of data
Explanation:
A snitch in Cassandra determines network topology and helps nodes decide where to store and retrieve data.
23. What is the default consistency level for read operations in Cassandra?
- ONE
- QUORUM
- ALL
- TWO
Answer: A) ONE
Explanation:
By default, Cassandra ensures that at least one replica returns data for read operations when the consistency level is set to ONE.
24. What is the purpose of hints in Cassandra?
- To provide query suggestions
- To temporarily store data for unavailable nodes
- To optimize indexing
- To track schema changes
Answer: B) To temporarily store data for unavailable nodes
Explanation:
Hints allow Cassandra to store updates temporarily when a node is down and deliver them once the node is back online.
25. How does Cassandra achieve linear scalability?
- By adding more nodes to the cluster
- By increasing CPU power on existing nodes
- By using master-slave replication
- By enforcing strict schema constraints
Answer: A) By adding more nodes to the cluster
Explanation:
Cassandra scales horizontally, meaning performance improves as more nodes are added to the cluster.
26. Which of the following best describes a materialized view in Cassandra?
- A static snapshot of a table
- A precomputed view that supports fast queries
- A primary key constraint enforcement tool
- A mechanism for automatic schema changes
Answer: B) A precomputed view that supports fast queries
Explanation:
Materialized views in Cassandra allow efficient querying of data by storing precomputed views with different primary keys.
27. How does Cassandra handle schema evolution?
- By requiring downtime for schema changes
- By using schema-on-read
- By allowing dynamic schema changes
- By enforcing strict constraints
Answer: C) By allowing dynamic schema changes
Explanation:
Cassandra supports dynamic schema changes without downtime, allowing easy modification of tables.
28. What is the purpose of secondary indexes in Cassandra?
- To enable fast lookups on non-primary key columns
- To replace partition keys
- To enhance data encryption
- To manage data replication
Answer: A) To enable fast lookups on non-primary key columns
Explanation:
Secondary indexes in Cassandra allow efficient searching of non-primary key columns.
29. Which command is used to delete a table in Cassandra?
- DROP TABLE
- DELETE TABLE
- REMOVE TABLE
- TRUNCATE TABLE
Answer: A) DROP TABLE
Explanation:
The DROP TABLE command removes a table and all its associated data from Cassandra.
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