Hands-on lab: Implementing Web Identity Federation for Cross-Platform Mobile App Data Storage with AWS DynamoDB and Fine-Grained Access Control

. Here, I’ll provide a step-by-step guide along with AWS CLI commands and explain the parameters in detail.

1. Create a DynamoDB Table:

aws dynamodb create-table --table-name UserPreferences --attribute-definitions AttributeName=UserID,AttributeType=S AttributeName=PreferenceData,AttributeType=S --key-schema AttributeName=UserID,KeyType=HASH AttributeName=PreferenceData,KeyType=RANGE --provisioned-throughput ReadCapacityUnits=5,WriteCapacityUnits=5


  • --table-name: The name of the DynamoDB table.
  • --attribute-definitions: Define the table’s attributes with their data types. In this case, UserID and PreferenceData are defined as strings.
  • --key-schema: Specifies the primary key structure. UserID is the partition key (HASH) and PreferenceData is the sort key (RANGE).
  • --provisioned-throughput: Set the initial read and write capacity units for the table.

2. Create IAM Role for Web Identity Federation:

aws iam create-role --role-name MobileAppRole --assume-role-policy-document '{
  "Version": "2012-10-17",
  "Statement": [
      "Effect": "Allow",
      "Principal": {
        "Federated": "cognito-identity.amazonaws.com"
      "Action": "sts:AssumeRoleWithWebIdentity",
      "Condition": {
        "StringEquals": {
          "cognito-identity.amazonaws.com:aud": "YOUR_COGNITO_IDENTITY_POOL_ID"


  • --role-name: The name of the IAM role.
  • --assume-role-policy-document: This policy document specifies that the role can be assumed by Cognito Identity with a specific audience (your Cognito Identity Pool ID).

3. Attach Policies to the IAM Role:

You would typically attach policies to this role that define the permissions for accessing DynamoDB resources. You can create a custom policy and attach it to the role.

4. Configure Fine-Grained Access Control (FGAC) in DynamoDB:

This requires you to define policies that specify access control at the item or attribute level based on user identities, but it’s beyond the scope of a single CLI command and typically requires interaction with AWS services directly through the console or SDK.

5. Use Security Token Service (STS) to Get Temporary Credentials:

In your mobile app, you will use AWS SDKs to request temporary credentials for the role you’ve created (MobileAppRole). The CLI does not directly provide this functionality; it’s typically done in the mobile app’s code.

6. Mobile App Implementation:

Implement the mobile app’s authentication and data retrieval logic using the AWS SDKs (e.g., AWS Amplify, AWS Mobile SDK for Android/iOS). Use the temporary credentials obtained in step 5 to make authenticated requests to DynamoDB.

Remember to replace placeholders like YOUR_COGNITO_IDENTITY_POOL_ID with your actual values in the above commands.

This explanation covers the AWS CLI commands for setting up the infrastructure components. The actual mobile app implementation and FGAC policies would require using the AWS SDKs and additional configurations beyond what the CLI provides.

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