//Let "id" and "name" are the column names inside DynamoDB table.
//It contains a entry having id=2 and name="abc"
//Following are the fields you need mention in form to get the entries from table id having value 2.
#a = :id_val //KeyConditionExpression
{"#a":"id" } //ExpressionAttributeNames
{":id_val":2} //ExpressionAttributeValues