{"id":"dynamodb-updateitem-upsert-behavior","text":"DynamoDB `UpdateItem` creates the item if the primary key doesn't exist (upsert behavior); otherwise it modifies the existing item's attributes.","truth_value":"IN","source":"entries/2026/03/11/amazondynamodb-latest-APIReference-API_UpdateItemhtml.md","source_url":"","source_hash":"3e4e050a17f9475f","justifications":[],"dependents":[],"metadata":{},"explanation":{"steps":[{"node":"dynamodb-updateitem-upsert-behavior","truth_value":"IN","reason":"premise"}]}}