What is the role of transactions in working with databases and why are they important?

Transactions in databases ensure that a set of operations are executed as a single unit. This means that either all operations within a transaction are successfully completed, or none are applied (rollback). This is important for maintaining data integrity and preventing errors during failures or concurrent access.

The main properties of transactions are described by the acronym ACID:

• Atomicity — all operations of a transaction are completed fully or not at all.
• Consistency — a transaction brings the database from one valid state to another.
• Isolation — concurrent transactions do not affect each other.
• Durability — after a transaction is committed, its changes are saved even in case of failures.

In Node.js, when working with databases (for example, through libraries like Sequelize, TypeORM, or directly with drivers), transactions guarantee that complex data operations are performed correctly and without data loss.