What is ACID? What databases have you worked with?

ACID is a set of properties of transactions in databases that ensure reliability and correctness of operations:

• Atomicity: a transaction is either fully completed or not executed at all.
• Consistency: after a transaction completes, the database remains in a correct state, satisfying all constraints.
• Isolation: concurrent transactions do not affect each other, and the result is equivalent to sequential execution.
• Durability: after a transaction is committed, changes are saved even in case of failures.

In my work, I used relational databases such as PostgreSQL and MySQL, which support ACID transactions. I also have experience with NoSQL databases, such as MongoDB, where ACID support is limited to individual documents.