SQL vs NoSQL Databases: Architecture, ACID Compliance & Speed Comparison

SQL databases (PostgreSQL, MySQL) are relational, table-based systems enforcing rigid schemas and ACID transactions. NoSQL databases (MongoDB, DynamoDB, Redis) provide flexible document, key-value, or graph schemas optimized for horizontal scale.

Architectural Verdict

Choose SQL (PostgreSQL is standard modern choice) as the default database for most applications due to robust ACID transactions and rich query power. Choose NoSQL for specialized horizontal scale, caching, or unshaped document storage.