AWS DVA-C02 Drill: DynamoDB Fine-Grained Access Control - Role Condition Constraints

Jeff’s Note

#

Unlike generic exam dumps, ADH analyzes this scenario through the lens of a Real-World Lead Developer.

For DVA-C02 candidates, the confusion often lies in how to apply attribute-and-key-level IAM restrictions using web identity federation variables. In production, this is about knowing exactly how to craft IAM policy conditions that prevent unauthorized attribute changes while enabling scoped access. Let’s drill down.

The Certification Drill (Simulated Question)

#

Scenario

#

A mobile fitness tracking app called FitPulse stores user profiles in an Amazon DynamoDB table with four attributes: member_id, member_name, fitness_score, and fitness_rank. Users can only update their own member_name. Authentication is done using a web identity federation provider (like Facebook or Google).

The Requirement:

#

You want to create an IAM role policy condition that allows users to call the dynamodb:PutItem API only if they update their own item identified by their unique member_id, and the only attribute they can change is member_name.

The Options

#

• A) "ForAllValues:StringEquals": {"dynamodb:LeadingKeys": ["${www.amazon.com:member_id}"], "dynamodb:Attributes": ["member_name"]}
• B) "ForAllValues:StringEquals": {"dynamodb:LeadingKeys": ["${www.amazon.com:member_name}"], "dynamodb:Attributes": ["member_id"]}
• C) "ForAllValues:StringEquals": {"dynamodb:LeadingKeys": ["${www.amazon.com:member_id}"], "dynamodb:Attributes": ["member_name","member_id"]}
• D) "ForAllValues:StringEquals": {"dynamodb:LeadingKeys": ["${www.amazon.com:member_name}"], "dynamodb:Attributes": ["member_name","member_id"]}

Google adsense

#

leave a comment:

Correct Answer

#

A.

Quick Insight: The Developer Imperative

#

For DVA-C02, precisely controlling user updates via IAM condition keys like dynamodb:LeadingKeys and dynamodb:Attributes is essential for applying least privilege. The principal variable ${www.amazon.com:member_id} corresponds to the authenticated user’s ID via federation, ensuring users can update only their own partition key. Restricting attributes to "member_name" prevents unauthorized changes to fitness_score or fitness_rank.

Content Locked: The Expert Analysis

#

You’ve identified the answer. But do you know the implementation details that separate a Junior from a Senior?

The Expert’s Analysis

#

Correct Answer

#

Option A

The Winning Logic

#

Option A correctly ties the dynamodb:LeadingKeys condition to the user’s identity ${www.amazon.com:member_id}, meaning the operation is only allowed on the item whose partition key matches the authenticated user. Additionally, it restricts the PutItem call to modify only the member_name attribute, preventing unauthorized updates to fitness_score or fitness_rank. This enforces fine-grained security via IAM.

• The ForAllValues:StringEquals operator states all leading keys and attributes in the request must match the listed values.
• Using the web identity token variable ${www.amazon.com:member_id} is critical because the ID comes from the authenticator, ensuring user scoping.
• Limiting the dynamodb:Attributes condition to a single attribute ensures only the allowed one is updated.

The Trap (Distractor Analysis):

#

• Option B: Uses ${www.amazon.com:member_name} as leading key, which is inaccurate. The partition key is member_id, not member_name. This causes the condition to fail regardless of the real user ID.
• Option C: Allows the user to update both member_name and member_id attributes. Allowing changes to the partition key value compromises data integrity and authorization boundaries.
• Option D: Similar to B, leading key references member_name instead of member_id, and it allows multiple attributes update, compounding both errors.

The Technical Blueprint

#

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": "dynamodb:PutItem",
      "Resource": "arn:aws:dynamodb:region:account-id:table/FitPulseUsers",
      "Condition": {
        "ForAllValues:StringEquals": {
          "dynamodb:LeadingKeys": ["${www.amazon.com:member_id}"],
          "dynamodb:Attributes": ["member_name"]
        }
      }
    }
  ]
}

The Comparative Analysis

#

Real-World Application (Practitioner Insight)

#

Exam Rule

#

For the exam, always map the partition key to the federated user ID variable in the IAM policy condition when restricting DynamoDB PutItem access, and limit writable attributes explicitly.

Real World

#

In production, this approach enables multi-tenant SaaS apps to safely expose a single table to many users without risking data leakage or unintended overwrites. Using identity federation variables in condition keys is critical for scalable fine-grained access control.

(CTA) Stop Guessing, Start Mastering

#

Disclaimer

This is a study note based on simulated scenarios for the AWS DVA-C02 exam.