Scan Function in DynamoDB with reserved keyword as FilterExpression NodeJS

:status is a placeholder in your expression that you aren't providing a value for. See how you are providing values for your other placeholders here:

expressionAttr[":delivered"] = "delivered";
expressionAttr[":bad"] = "bad";
expressionAttr[":void"] = "void"

You need to do the same for the :status placeholder. I don't see anything about a reserved word in the error message, so I'm not sure why you think that's the cause of the error. The error very specifically states that you aren't providing a value for the :status placeholder.

Solved :

There are two parameters taken by aws-sdk :

Expression Attribute Name

Expression Attribute Value

both provide the functionality of replacing placeholders used in the attributes list. Here by Attributes it is a bit ambiguous, where I got confused. The wizards over at aws mean both the key and value when they use the term attribute.

So in a case where you want to use a reserved key word as a key attribute use the Expression Attribute Name parameter with #(pound) to denote the placeholder.

Similarly where you want to use placeholders for value attribute use the Expression Attribute Value parameter with :(colon) to denote the placeholder.

So finally my code (working) looks like this :

var param = {
  TableName: "faasos_orders",
  FilterExpression: "#order_status = :delivered OR #order_status = :void OR #order_status = :bad",
  ExpressionAttributeValues: {
    ":delivered": "delivered",
    ":void": "void",
    ":bad": "bad"
  },
  ExpressionAttributeNames: {
    "#order_status": "status"
  }
};  
  dynamodb.scan(param, function (err, data) {....});