NoSQL Database overview

Non-relational databases that trade ACID transactions and rigid schemas for flexible data models, horizontal scalability, and high write throughput. Sub-categories include document stores (MongoDB, Firestore), key-value stores (DynamoDB, Redis), wide-column stores (Cassandra, ScyllaDB), and eventually-consistent distributed databases. Best suited for workloads with heterogeneous record shapes, massive scale-out requirements, or access patterns that fit a single-document or single-key read. Often paired with a relational DB for structured transactional data. Schema validation, indexing strategies, and consistency tuning are key operational concerns.