Cassandra Interview Questions & Answers Part 1

In this tutorial, let’s look at the 1st set of interview questions and answers on Cassandra.

1. What is Cassandra?

Cassandra is a highly scalable, distributed NoSQL database management system designed for managing large volumes of structured, semi-structured, and unstructured data across commodity servers.

2. What are the advantages of using Cassandra over a traditional RDBMS?

Some advantages of using Cassandra over a traditional RDBMS include:

• Highly scalable architecture that can easily handle large volumes of data
• High availability and fault tolerance with no single point of failure
• No fixed schema, allowing for flexible data modeling and easy adaptation to changing data requirements
• Built-in support for multi-datacenter replication
• High write and read throughput with low latency

3. What are the disadvantages of using Cassandra?

Some disadvantages of using Cassandra include:

• No support for joins, transactions, and complex queries
• Limited support for ad-hoc queries and reporting
• Complex data modeling and query optimization
• Higher learning curve for developers compared to traditional RDBMS

4. What is a cluster in Cassandra?

A Cassandra cluster is a group of nodes that work together to store and manage data. A cluster can span multiple datacenters and can be configured for replication between datacenters.

5. What is a node in Cassandra?

A node in Cassandra is a single server in the cluster that stores a subset of the data. Each node communicates with other nodes in the cluster to ensure that data is distributed and replicated across the system.

6. What is a partition key in Cassandra?

A partition key in Cassandra is a value that determines the node on which a row of data is stored. Cassandra uses partition keys to distribute data across the nodes in the cluster.

7. What is a token in Cassandra?

A token in Cassandra is a randomly generated identifier that is used to determine the location of data within the cluster. Each node is assigned a range of tokens, and data is stored on the node whose token range includes the token value of the data.

8. What is replication factor in Cassandra?

Replication factor is the number of copies of data that are stored in the cluster. A higher replication factor provides higher availability and fault tolerance, but also increases the storage requirements.

9. What is the consistency level in Cassandra?

Consistency level in Cassandra determines how many nodes must acknowledge a read or write operation before it is considered successful. Higher consistency levels provide stronger data consistency guarantees, but may impact performance and availability.

10. What is compaction in Cassandra?

Compaction in Cassandra is the process of merging SSTables to reclaim disk space and improve read performance. There are two types of compaction: minor and major. Minor compaction merges small SSTables to reduce the number of files on disk, while major compaction merges all SSTables to remove obsolete data and reduce the storage requirements.

11. What is a super column in Cassandra?

A super column in Cassandra is a way to group related columns together. It is deprecated in newer versions of Cassandra in favor of composite columns.

12. What is a composite column in Cassandra?

A composite column in Cassandra is a column that has multiple components, each with its own name and value. Composite columns are used to represent complex data structures in a single column.

13. What is a secondary index in Cassandra?

A secondary index in Cassandra is an index that is created on a non-primary key column. It allows for faster querying of data based on columns other than the primary key.

14. What is a tombstone in Cassandra?

A tombstone in Cassandra is a marker that is placed on a row to indicate that it has been deleted. Tombstones are used to ensure data consistency and are removed during compaction.

15. What is a batch statement in Cassandra?

A batch statement in Cassandra is a way to group multiple data modification statements together into a single atomic operation. This ensures that either all the modifications are successful or none of them are.

16. What is hinted handoff in Cassandra?

Hinted handoff in Cassandra is the process of temporarily storing write requests on other nodes if the primary node for a particular partition is unavailable. When the primary node becomes available again, the stored requests are sent to it for processing.

17. What is a snitch in Cassandra?

A snitch in Cassandra is a component that determines the topology of the cluster and how nodes are distributed across datacenters. The snitch is responsible for helping Cassandra determine the best nodes to read and write data from.

18. What is a commit log in Cassandra?

A commit log in Cassandra is a file that stores all modifications made to data in the database. It is used to ensure data durability and is replayed in case of node failures.

19. What is hinted handoff in Cassandra?

Hinted handoff in Cassandra is the process of temporarily storing write requests on other nodes if the primary node for a particular partition is unavailable. When the primary node becomes available again, the stored requests are sent to it for processing.

20. What is a gossip protocol in Cassandra?

The gossip protocol in Cassandra is a decentralized protocol that is used for communication between nodes in the cluster. It is responsible for disseminating information about the cluster’s topology, status, and other metadata.

21. What is a compaction in Cassandra?

Compaction in Cassandra is the process of merging multiple SSTables into a single SSTable to reduce disk usage and improve read performance.

22. What is a read repair in Cassandra?

A read repair in Cassandra is a process that automatically repairs inconsistencies between replicas of data during read operations. It ensures data consistency across the cluster.

23. What is a hinted handoff in Cassandra?

Hinted handoff in Cassandra is the process of temporarily storing write requests on other nodes if the primary node for a particular partition is unavailable. When the primary node becomes available again, the stored requests are sent to it for processing.

24. What is a batch statement in Cassandra?

A batch statement in Cassandra is a way to group multiple data modification statements together into a single atomic operation. This ensures that either all the modifications are successful or none of them are.

25. What is the purpose of a replication factor in Cassandra?

The replication factor in Cassandra specifies the number of nodes that should store copies of each piece of data. This ensures that data is replicated across the cluster for redundancy and fault tolerance.

26. What is the difference between a row and a partition in Cassandra?

In Cassandra, a row is the smallest unit of data and consists of a key and one or more columns. A partition is a collection of rows that share the same partition key. Partitions are stored on a single node in the cluster.

27. What is a token in Cassandra?

A token in Cassandra is a numerical value that represents a position in the ring. Tokens are used to determine which node in the cluster is responsible for storing a particular partition.

28. What is a cluster in Cassandra?

A cluster in Cassandra is a collection of nodes that work together to store and manage data. A cluster can span multiple datacenters and regions for geographic distribution.

29. What is the role of the snitch in Cassandra?

The snitch in Cassandra is responsible for determining the topology of the cluster and how nodes are distributed across datacenters. It helps Cassandra determine the best nodes to read and write data from.

30. What is a SSTable in Cassandra?

A SSTable in Cassandra is an immutable, on-disk data structure that contains sorted data for a particular partition range. SSTables are used for data storage and are periodically merged during compaction.