Apache Cassandra Fundamentals

Apache Cassandra is a distributed NoSQL database designed for high write throughput and availability across multiple data centers. It uses a peer-to-peer architecture with tunable consistency, making it suited for workloads that prioritize uptime and horizontal scalability over strong transactional guarantees.

itDatabases and data storage

Apache Cassandra Fundamentals

Apache Cassandra is an open-source, distributed NoSQL database. It stores data across a cluster instead of making one server the permanent center of every operation.

That design serves a specific need. Some applications must keep accepting reads and writes as data volume grows or individual machines fail. Cassandra distributes partitions, keeps replicas, and lets any suitable node coordinate a request.

Cassandra is not a general replacement for a relational database. It favors predictable, partition-oriented access over joins and cross-partition transactions. You get the most value when you know the application's queries before you design its tables.

The core mental model

Think in three layers:

The data model turns an application query into a table and primary key.
The cluster maps each partition to a token range and stores replicas on several nodes.
The storage engine records each write in a commit log and memtable, then flushes immutable SSTables to disk.

A client can contact any node. That node becomes the coordinator for the request. The coordinator finds the replicas for the partition, sends the request, and waits for enough replica responses to satisfy the chosen consistency level.

No node owns a special primary-server role for the whole database. Replicas can accept mutations for the token ranges they hold. This multi-primary structure helps Cassandra continue operating through node failures.

Apache Cassandra Fundamentals

The core mental model

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