Condition Expressions – Amazon DynamoDB

To manipulate data in an Amazon DynamoDB table, you use the PutItem, UpdateItem, and DeleteItem operations. (You can also use BatchWriteItem to perform multiple PutItem or DeleteItem operations in a single call.) For these data manipulation operations, you can specify a condition expression to determine which items should be modified.

https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.ConditionExpressions.html