Apache Cassandra

Open-source NoSQL distributed database built for high availability and horizontal scalability across commodity hardware or cloud infrastructure. Uses a masterless architecture with no single points of failure, so reads and writes can continue even when an entire data center goes down.

Trusted by enterprises such as Netflix, Bloomberg, and Backblaze for mission-critical workloads. Bloomberg serves over 20 billion requests per day on a nearly 1 PB dataset across more than 1,700 nodes. Stands out from other NoSQL stores with best-in-class multi-datacenter replication, tunable consistency per query, and linear throughput scaling as new nodes are added.

Key capabilities:

• Masterless, peer-to-peer architecture with no network bottlenecks
• Multi-datacenter replication and fault tolerance with support for regional failover
• Tunable consistency: choose between synchronous or asynchronous replication per operation
• CQL, a SQL-like query language for schema and data access
• Linear scalability for both reads and writes as the cluster grows
• Audit logging and workload capture for operators

Use cases: time-series and metrics storage, user sessions and activity streams, product catalogs, IoT sensor data, and financial transaction logs. Fits teams running high-write workloads that need geographic distribution, low-latency access across regions, or the ability to survive data center outages without data loss.