What is the difference between SQL and NoSQL databases? SQL databases are relational; NoSQL databases are non-relational and can store unstructured data. When would you choose a NoSQL database over SQL? When dealing with large volumes of unstructured or semi-structured data requiring scalability. What is ACID in databases? Atomicity, Consistency, Isolation, Durability – properties ensuring reliable transactions. How do you handle database migrations? Using tools like migrate or mongoose for schema changes over time