ACID (Atomicity, Consistency, Isolation, Durability) is a set of properties that guarantee that database transactions are processed reliably. ACID is a concept in database systems that refers to a set of properties that a transaction should have to be considered “valid.”

• Atomicity: All the operations in a transaction are considered as a single unit of work, which means that either all operations in a transaction must succeed, or none of them should be applied to the database. It guarantees that the transaction is completed in its entirety or not at all.
• Consistency: A transaction moves the database from one consistent state to another, so it must preserve the integrity constraints and the consistency of the data. In other words, the database should be consistent before and after a transaction is executed.
• Isolation: Transactions execute in isolation from other transactions. This means that concurrent transactions do not interfere with each other.
• Durability: Once a transaction has been committed, it is permanent and should survive any subsequent system failures, such as power outages or crashes.

The ACID properties are important for maintaining data consistency and ensuring the reliability of transactions in a database.

Distributed Applications

In distributed applications, ACID transactions become more complex because they need to maintain consistency and correctness across multiple nodes or systems. Traditional ACID transactions rely on a single database and a single transaction manager to coordinate and manage the transactions. In a distributed environment, multiple databases or services may need to participate in a single transaction, and a distributed transaction manager must coordinate these actions to ensure that the transaction maintains its ACID properties.

Distributed transactions require additional coordination to ensure that all participants agree on the outcome of the transaction. For example, a two-phase commit protocol may be used to ensure that all participants are ready to commit the transaction before it is committed, and to roll back the transaction if any participant fails to commit.

However, the use of distributed transactions can also introduce additional complexity and performance overhead, and may not be suitable for all applications. In some cases, alternative approaches such as eventual consistency or compensation-based transactions may be used.