Are there conditions under which DynamoDB allows for a duplicate primary key?

Question

While performing an updateItem operation to a dynamo table using the AWS Javascript SDK, I am instead seeing a second row written with the same primary key, which certainly seems contrary to the documentation.

I am using a hash string key "user_id".

The initial write:

var params = {
  Item: {
    user_id : {S: "foo"},
    is_authorized: {BOOL: false},
  },
  TableName: 'MyTable'
};
db.putItem(params, function(err, data){
  if(err){
    console.log(err);
  }else{
    console.log(data);
  }
});

The Update Attempt

var updateParams = {
  Key: {
    user_id : {S: "foo"},
  },
  AttributeUpdates: {
    confirmationCode: {Action: "PUT", Value: {S: "key"}},
    phone: {Action: 'PUT', Value: {S: "1234567}},
    is_authorized: {Action: 'PUT', Value: {BOOL: false}},
    confirmAttempts: {Action: 'PUT', Value: {N: "1"}}
  },
  TableName: 'MyTable'
};

db.updateItem(params, function(err, data){
  if(err){
    response = err;
    console.log("The error was: " + err);
  }else{
    response = data;
    console.log(data);
  }
});

Answer 1

For reference to others who might come across this issue:

This issue was caused by whitespace, specifically a trailing space at the end of some primary key strings. Viewing Dynamo records, at least from within the console, does not convert whitespace characters, so it was an invisible issue.