Are multi-document operations inherently atomic?

In MongoDB, multi-document operations are not inherently atomic. This means that when you perform operations that affect multiple documents, each operation on an individual document may succeed or fail independently of the others.

MongoDB ensures atomicity at the single-document level, which means that when an update or write operation is performed on a single document, it will either complete fully or not at all. This is important for maintaining data integrity within that document. However, when it comes to operations involving multiple documents, such as transactions that affect several documents or collections simultaneously, they do not have the same atomic guarantees unless specific transactional capabilities are utilized.

Historically, operations that span multiple documents within MongoDB lacked atomicity, so changes could result in partial updates or inconsistencies. In such cases, if an application encountered an error partway through a multi-document operation, some operations might be applied while others were not, leading to potential data integrity issues.

It's essential to note that MongoDB introduced support for multi-document transactions, but these transactions exist within a specific set of conditions and overhead. Thus, while you can achieve atomicity across multiple documents using transactions, it's not a guaranteed characteristic for all multi-document operations by default. This addition allows for multi-document operations to be atomic