Answer
MongoDB uses timestamp-based MVCC. Conflicting writes trigger transaction abort to maintain isolation guarantees.
Quick Answer
Under snapshot isolation, if two concurrent transactions write to the same document, the second to commit gets a WriteConflict error and must retry. WiredTiger detects this at commit time by checking if the document was modified after the transaction's snapshot timestamp. This is optimistic concurrency - no locks taken for reads, conflicts detected at commit.
S
SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
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Source: SugharaIQ