Which characteristic is commonly associated with NoSQL databases?

• A. Rigid schema with strict ACID transactions.
• B. Fixed, vertically scalable architecture.
• C. Flexible schema with eventual consistency and scalability.
• D. Automatic relational joins across tables.

Answer: (C)

NoSQL databases are commonly associated with a flexible schema coupled with eventual consistency and scalable performance. This means data can be stored without a fixed table structure, allowing the schema to evolve as requirements change. At the same time, NoSQL systems are designed to scale horizontally across many machines, making it easier to handle growing workloads. They often adopt eventual consistency rather than immediate strict consistency to achieve high availability and partition tolerance, staying responsive even when parts of the system are serving requests. This combination—flexible schema, eventual consistency, and scalable architecture—best reflects how NoSQL databases are typically used. The other descriptions describe relational databases or architectures that rely on rigid schemas, strong ACID guarantees, or complex joins, which are not defining traits of NoSQL systems.