ACID Properties in MongoDB

ACID Properties ensures the integrity and reliability of the database. The term ACID stands for Atomicity, Consistency, Isolation, and Durability. Let’s understand each of these ACID transaction properties with their examples.

1. Atomicity

It states that all the operations of the transaction take place at once and if not then the transaction is aborted. Transaction can not occur partially. Either all of the operations transactions are executed properly in a database or none of them will execute.

Example: Ensuring Atomicity in Bank Transactions

Consider a bank transaction where money is transferred from one account to another. Atomicity ensures that if the debit operation from one account succeeds, the corresponding credit operation to the other account also succeeds. If any failure occurs during the transfer (for example, a system crash), the transaction is rolled back, and both accounts retain their original balances.

2. Consistency

The integrity constraints must be maintained before and after the transaction. The consistency in transactions ensures that before and after the transaction operations the database remains in a valid state. The database must be consistent after the transaction happens.

Example: Maintaining Grade Integrity

In such a database, when we want to update a student’s grade using some transaction, the consistency concept guarantees that the updated grade value is always within the valid range (for instance, A, B, C, D, F) before and after the update. If the update violates any constraints (for example, assigning an invalid grade), the transaction is aborted to maintain consistency.

3. Isolation

Isolation is one of the ACID properties that ensures that transactions are executed independently of each other without interference. Changes occurring in a particular transaction will not be visible to any other transaction. Isolation guarantees that the changes made by one transaction are not visible to other transactions until the transaction is committed.

Example: Ensuring Transaction Integrity

Suppose there are two transactions: Transaction A transfers money from Account X to Account Y, while Transaction B queries the balance of Account Y. Isolation causes the state of the committed Account Y either before or after transaction A to be visible to Transaction B, without consideration of whether transaction A has already completed. It prevents Transaction B from seeing any intermediate, uncommitted state of Account Y caused by Transaction A.

4. Durability

This property is used to indicate the performance of the database’s consistent state. It states that after the transaction completes successfully the changes it has made to the database are permanent even if there are system failures.

Example: Transaction Persistence and Recovery

Once the transaction of fund transfer is effected smoothly on a banking system interface, the resilient feature makes it possible for the transaction input data to be stored and saved permanently in the system database regardless of the system crash that follows immediately after the transaction. When the system restarts, it should be able to recover the committed changes and restore the database to its last consistent state.

MongoDB ACID transactions are fundamental for ensuring data integrity in database transactions. In MongoDB, ACID properties play a crucial role in maintaining the reliability and consistency of data operations.

In this article, We will learn about ACID transactions in MongoDB, understand their importance with examples, and see how the transaction works in MongoDB along with their use cases.