Curriculum
In this tutorial, let’s look at the 1st set of interview questions and answers on 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.
Some advantages of using Cassandra over a traditional RDBMS include:
Some disadvantages of using Cassandra include:
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Compaction in Cassandra is the process of merging multiple SSTables into a single SSTable to reduce disk usage and improve read performance.
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.
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.
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.
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.
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.
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.
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.
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.
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.