Cassandra is a real-time database that supports single-digit millisecond response times at any scale. It is known for very fast writes, fast reads and nearly linear scalability. As Cassandra scales horizontally, doubling the number of nodes results in doubling the throughput and capacity of a database.

Cassandra is famous for high availability that mission-critical applications require. The key Cassandra design features that contribute to availability include:

• Peer-to-peer architecture with no single point of failure
• Fault-tolerance via replication and tunable consistency
• Best-in-class multi-datacenter support
• No downtime or interruption due to node maintenance

Cassandra is built to run in any cloud, while being independent from any single cloud provider ecosystem. Cassandra is an ideal choice for multi-cloud and hybrid-cloud deployments, where different datacenters of the same Cassandra cluster run in different clouds or use a combination of cloud and on-prem environments.

Cassandra Query Language (CQL) is the primary language for interacting with a Cassandra database. CQL is a declarative language with an SQL-like syntax, which makes it easy to learn. Examples of CQL statements include CREATE TABLE, INSERT, UPDATE, DELETE and SELECT. We will be able to try out some of these statements shortly.

Here we use a simple set of instructions to install Cassandra without any additional configuration.

Download and install Cassandra:

wget https://downloads.apache.org/cassandra/4.0-beta2/apache-cassandra-4.0-beta2-bin.tar.gz

tar -xzf apache-cassandra-4.0-beta2-bin.tar.gz

mv apache-cassandra-4.0-beta2 /usr/share/cassandra
rm apache-cassandra-4.0-beta2-bin.tar.gz

export PATH="$PATH:/usr/share/cassandra/bin:/usr/share/cassandra/tools/bin"

Start Cassandra:

cassandra -R

The -R flag allows the root user to run Cassandra. Running Cassandra as a non-root user does not need this flag.

Check the status of Cassandra:

nodetool status

The status/state column in the output should report UN, which stands for Up/Normal.

We use the CQL shell, a command-line client, to connect to Cassandra and execute CQL statements.

Start the CQL shell:

cqlsh

Create the keyspace, table and row in Cassandra:

CREATE KEYSPACE killr_video
WITH replication = {
  'class': 'SimpleStrategy', 
  'replication_factor': 1 };

USE killr_video;

CREATE TABLE users (
  email TEXT PRIMARY KEY,
  name TEXT,
  age INT,
  date_joined DATE
);

INSERT INTO users (email, name, age, date_joined) 
VALUES ('[email protected]', 'Joe', 25, '2020-01-01');

Retrieve the row from Cassandra:

SELECT * FROM users
WHERE email = '[email protected]';

Here is a short quiz for you.