DynamoDBContextConfig config = new DynamoDBContextConfig()
{
    ConsistentRead = false,
    Conversion =  DynamoDBEntryConversion.V2
};

using (DynamoDBContext context = new DynamoDBContext(config))
{
    long unixTimestamp = (long)(DateTime.UtcNow.Subtract(new DateTime(1970, 1, 1))).TotalSeconds;
    QTrackStatus qTrackStatus = new QTrackStatus()
    {
        Key = "m@m.com",
        EventCode = "CC",
        EventDateTime = "2019-09-09 14:00:30",
        EventLocation = "BFS",
        EventLastUpdate = unixTimestamp
    };

    DynamoDBOperationConfig dynamoDBOperationConfig = new DynamoDBOperationConfig()
    {
        QueryFilter = new List<ScanCondition>()
        {
            { new ScanCondition("EventCode", ScanOperator.NotEqual, "CC") }
        },
        ConditionalOperator = ConditionalOperatorValues.And
    };

    await context.SaveAsync(qTrackStatus, dynamoDBOperationConfig);
}