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 and where to enforce multi-factor authentication for user identities. In production, this is about knowing exactly which AWS services are designed to handle app user authentication and MFA versus infrastructure IAM users. Let’s drill down.
The Certification Drill (Simulated Question) #
Scenario #
A startup called StreamFlow is building a new social networking mobile app that requires robust user authentication with multi-factor authentication (MFA) support. The development team wants a highly scalable, secure, and user-friendly authentication system integrated tightly with the app.
The Requirement: #
Design the authentication architecture to implement MFA for app users with minimal developer overhead and scalable user management.
The Options #
- A) Use Amazon Cognito to create a user pool and create user accounts in that pool.
- B) Send MFA text codes manually by publishing SMS messages using the Amazon SNS Publish API from the mobile app code.
- C) Enable multi-factor authentication within the Amazon Cognito user pool settings.
- D) Use AWS IAM to create IAM users for each app user.
- E) Enable MFA for the IAM users created in AWS IAM.
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leave a comment:
Correct Answer #
A and C.
Quick Insight: The Developer Authentication Imperative #
Implementing MFA for mobile app end users must leverage a dedicated service designed for user authentication flows — that’s Amazon Cognito user pools. Trying to use IAM users for app users or manually handling MFA with SNS Publish APIs leads to maintenance overhead, security issues, and scaling nightmares.
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 #
Options A and C
The Winning Logic #
- Option A: Amazon Cognito user pools are purpose-built to manage app users, handle sign-up/sign-in flows, and integrate MFA easily without extra coding for SMS delivery or token validation. Creating users in Cognito user pools provides a scalable identity directory.
- Option C: MFA is a native feature you enable in Cognito user pools with a simple configuration toggle (optional or required, SMS or TOTP). This makes MFA seamless and secure for app users.
Using IAM users (Options D and E) is unsuitable since IAM is designed for granting permissions to AWS resources, not end users of an app. Managing thousands of IAM users for app logins is impractical and a security anti-pattern.
Sending MFA codes via Amazon SNS Publish API from the app (Option B) is also a poor practice — it requires custom code to generate, deliver, and verify MFA tokens, re-implementing what Cognito already provides out-of-the-box.
The Trap (Distractor Analysis): #
- Why not B? Sending MFA SMS via SNS Publish API adds complexity and security risk because the app manages MFA delivery and verification manually, increasing potential for errors and delays.
- Why not D or E? IAM users are for managing AWS resource access and are not designed for external app user authentication or MFA. This approach is not scalable or secure for application end users.
The Technical Blueprint #
# Example CLI commands to create Cognito user pool with MFA enabled:
# 1. Create user pool
aws cognito-idp create-user-pool --pool-name "StreamFlowUsers"
# 2. Enable MFA - set SMS and/or TOTP as required
aws cognito-idp set-user-pool-mfa-config \
--user-pool-id <user-pool-id> \
--mfa-configuration "ON" \
--sms-mfa-configuration "SmsAuthenticationMessage='Your code is {####}',SmsConfiguration={SnsCallerArn='<sns-role-arn>'}"
# Further integration with mobile app via AWS Amplify or SDK
The Comparative Analysis #
| Option | API Complexity | Performance | Use Case |
|---|---|---|---|
| A | Low - Managed by SDK | High - Scalable | User authentication, sign-up/sign-in flow management |
| B | High - Custom coding | Moderate | Manual MFA delivery, not recommended |
| C | Low - Config toggle | High | Enables MFA securely on Cognito users |
| D | N/A - Not app users | N/A | IAM users for AWS resource access, not app authentication |
| E | N/A | N/A | IAM user MFA for AWS resource security, irrelevant here |
Real-World Application (Practitioner Insight) #
Exam Rule #
For the exam, always pick Amazon Cognito user pools when implementing user authentication and MFA in mobile or web apps.
Real World #
In some custom scenarios, if you need full control over MFA delivery, third-party identity providers or custom auth flows with Lambda triggers might be used, but Cognito is the default best practice for most apps.
(CTA) Stop Guessing, Start Mastering #
Disclaimer
This is a study note based on simulated scenarios for the AWS DVA-C02 exam.