Sample AppSync Resolver for PutItem Operation including with Conflict Resolution

putitem-conflict-resolution.vtl

{
    "version" : "2017-02-28",
    "operation" : "PutItem",
    "key" : {
        "shopID" : $util.dynamodb.toDynamoDBJson($ctx.args.shopID),
        "id": $util.dynamodb.toDynamoDBJson($ctx.args.id)
    },
    "attributeValues" : {
        "staffName" : $util.dynamodb.toDynamoDBJson($ctx.args.staffName),
        "modifiedDate": $util.dynamodb.toDynamoDBJson($ctx.args.modifiedDate),
        "createdDate": $util.dynamodb.toDynamoDBJson($ctx.args.createdDate)
    },
    ## Conflict Resolution with modified date
    "condition" : {
        ## If old modifiedDate smaller than new modifiedDate ==> okay
        ## Else ==> error (Not Latest version)
        "expression" : "modifiedDate < :modifiedDate",
        "expressionValues" : {
            ":modifiedDate" : $util.dynamodb.toDynamoDBJson($ctx.args.modifiedDate)
        }
    }
}