Cassandra is a distributed non-relational database that can handle large chunks of unstructured data sets across many commodity servers. It’s a popular choice for individual developers as well as large enterprise companies.

Thanks to Cassandra’s distributed nature, there is no single point of failure. Instead, the data lives in many replica nodes throughout the database. If one of these nodes goes down, the rest of the system continues to run and the data remains secure. 


How Does Cassandra Work?

Cassandra is capable of handling huge amounts of data that live in cloud data centers. In case of data loss or failure in one of the nodes, the data throughout the rest of the system remains safe due to Cassandra’s distributed nature. This is all  thanks to the replica architecture of the database.

Cassandra’s Key Components

  1. Architecture
  2. Partitioning system
  3. Replicability

Let’s take a look at each of these components.

Cassandra in 100 Seconds. | Video: DataStax Developers


Cassandra’s Architecture

Cassandra is made up of a cluster of peer-to-peer network nodes. Each node in the Cassandra database has an equal amount of importance, which is the key aspect of Cassandra’s reliable structure.

A single Cassandra node is responsible for storing data and a group of these nodes is called a data center. These data centers combined form a cluster that is responsible for processing the data.

Even when you run out of space, Cassandra’s  structure makes it simple to add more storage. To house more data, all you need to do is add more nodes to the system. This process also goes the other direction: A developer can easily reduce the number of nodes to make the system tidier and reduce redundancies. This type of architecture gives Cassandra an advantage over SQL databases when it comes to housing data. While Cassandra allows for adding nodes on the fly, scaling a SQL database means taking the database down for a while, which limits user access.

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Cassandra’s Partitioning System

In Cassandra, a partitioning system stores, retrieves and chooses where to store the copy of the data. This happens by way of a partition key.

Each node in the database holds a token based on the partitioning key, which helps the system locate the data. When a client connects with the database, a coordinator node ensures the data gets to the right node. This happens with the help of the nodal tokens and a hash function of the partition key.


Cassandra’s Replicability

Another key function of Cassandra is replicating data to replica nodes. This feature makes the database less susceptible to data loss.

Cassandra uses the replication factor (RF) to specify the number of replicas to create. For example, an RF of three means there are three replicas for each data node.

This is the key to Cassandra’s reliability. If one node stops functioning, the data still exists in the replica nodes and you’re unlikely to ever lose data completely.

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