NoSQLDBMS

NoSQLDBMS is a class of database management systems that depart from the traditional relational model. They store and retrieve data without requiring a fixed table schema, and they emphasize horizontal scalability, fault tolerance, and flexible data models. NoSQL systems are designed to handle large volumes of data and high-velocity workloads across distributed clusters, often chosen for web-scale applications and real-time analytics. They are sometimes used alongside relational databases in polyglot architectures.

NoSQL databases are commonly categorized by data model into four broad types: key-value stores, document stores, wide-column stores (column-family), and graph databases. Key-value stores map keys to single values and are favored for simple, fast lookups. Document stores hold semi-structured documents, typically in JSON or similar formats, enabling nested structures. Wide-column stores organize data into column families and are efficient for sparse, denormalized data. Graph databases store entities as nodes and relationships as edges, enabling graph traversals for network queries.

Key characteristics include schema flexibility, eventual or tunable consistency models, and emphasis on partition tolerance and horizontal scaling. Many NoSQL DBMS provide distributed architectures with automatic sharding and replication. Transaction support ranges from single-document or single-operation atomicity to multi-document transactions in some systems, but strict ACID transactions are less universal than in relational systems.

Common use cases include content catalogs, user session stores, real-time analytics, social graphs, and IoT data streams. Notable examples include MongoDB (document), Cassandra (wide-column), Redis (key-value), and Neo4j (graph).