Cassandra
In plain terms
A distributed, highly-scalable wide-column NoSQL database.
Going deeper
Apache Cassandra spreads data across many nodes with no single point of failure, prioritizing availability and write throughput at massive scale. It excels at high write loads.
Under the hood
Tunable consistency, masterless ring architecture; you design tables around queries, not flexibility.
Examples
Time-series, IoT, messaging, Netflix/Instagram scale, high-write workloads.
Think of it like...
Like a leaderless team where any member can take an order and they reconcile later.