Discover the common pitfalls when integrating AWS Lambda with DynamoDB and learn how to ensure your Python functions perform flawlessly with our expert guide on permissions and configurations.
Table of Contents
Question
A developer has created an AWS Lambda function that is written in Python. The Lambda function reads data from objects in Amazon S3 and writes data to an Amazon DynamoDB table. The function is successfully invoked from an S3 event notification when an object is created. However, the function fails when it attempts to write to the DynamoDB table.
What is the MOST likely cause of this issue?
A. The Lambda function’s concurrency limit has been exceeded.
B. DynamoDB table requires a global secondary index (GSI) to support writes.
C. The Lambda function does not have IAM permissions to write to DynamoDB.
D. The DynamoDB table is not running in the same Availability Zone as the Lambda function.
Answer
C. The Lambda function does not have IAM permissions to write to DynamoDB.
Explanation
The correct answer to the question is C. The Lambda function does not have IAM permissions to write to DynamoDB.
The reason for this answer is that:
- Option C: The Lambda function does not have IAM permissions to write to DynamoDB is the most likely cause of this issue. To write data to an Amazon DynamoDB table from a Lambda function, the function needs to have IAM permissions to perform the PutItem, UpdateItem, or BatchWriteItem API actions on the table. These permissions are set via an IAM role that the function assumes when it is invoked. The role must have a policy that allows the function to access the DynamoDB table. If the role does not have the necessary permissions, the function will fail with an AccessDeniedException error when it tries to write to the table.
- Option A: The Lambda function’s concurrency limit has been exceeded is not a likely cause of this issue. The concurrency limit of a Lambda function is the number of instances of the function that can run at the same time. If the limit is exceeded, the function invocation will be throttled and return a ThrottlingException error. However, this error will occur before the function attempts to write to DynamoDB, not after.
- Option B: DynamoDB table requires a global secondary index (GSI) to support writes is not a valid cause of this issue. A global secondary index (GSI) is an optional feature of DynamoDB that allows you to create an alternative key for querying the table. A GSI does not affect the ability of a Lambda function to write data to the table. A Lambda function can write data to a table regardless of whether it has a GSI or not, as long as it has the appropriate permissions and provides the required attributes for the primary key of the table.
- Option D: The DynamoDB table is not running in the same Availability Zone as the Lambda function is not a relevant cause of this issue. The DynamoDB table and the Lambda function do not need to run in the same Availability Zone. DynamoDB is a regional service that replicates data across multiple Availability Zones within a region. Lambda functions can access DynamoDB tables in any Availability Zone within the same region, as long as they have network connectivity and permissions.
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