How can you guarantee that operations have ACID properties?

To guarantee that operations have ACID (Atomicity, Consistency, Isolation, Durability) properties in MongoDB, utilizing a multi-document transaction is the most effective approach. Multi-document transactions allow developers to bundle operations on multiple documents into a single, atomic operation. This means that either all operations within the transaction are executed successfully, ensuring consistency, or none are applied, which guarantees that the database does not reach an inconsistent state.

In a multi-document transaction, the system maintains isolation among transactions, meaning that concurrent transactions do not interfere with each other's operations. This ensures that any intermediate state is not visible to other operations, preserving the integrity of the data. The durability property ensures that once a transaction has been committed, its results will persist even in the event of a failure.

Using a primary key or a single document transaction only addresses atomicity and might not address scenarios where multiple documents need to be manipulated as part of a single logical operation. While using synchronous operations can improve reliability and control over the order of operations, it does not inherently guarantee ACID properties across multiple documents.

Therefore, the use of multi-document transactions is essential for ensuring that complex operations across multiple documents in MongoDB can uphold ACID properties, making it the correct choice for this