Amazon Web Services Updated DVA-C02 Exam Questions and Answers by tudor

The correct condition expression is attribute_not_exists(streamID) AND attribute_not_exists(seqID). This prevents PutItem from overwriting an item that already has the same composite primary key. In DynamoDB, PutItem normally replaces an existing item with the same primary key unless a condition expression blocks the operation. The option must reference the actual partition key and sort key attribute names, not generic words like PARTITION or SORT. The attribute_exists function would do the opposite: it would only allow the operation when those attributes already exist, which does not preserve uniqueness. AWS DynamoDB documentation explains that condition expressions with attribute_not_exists are used to prevent replacing existing items, and for composite keys the partition and sort key checks are evaluated together. ( AWS Documentation )

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The requirement is to analyze existing Lambda logs using a request ID that appears in both functions, and to do so with the least development effort . Amazon CloudWatch Logs Insights is purpose-built for interactive log analysis: it lets you run ad-hoc queries over CloudWatch log groups using a query language that supports filtering, parsing, sorting, and aggregation. This means you can quickly search across the relevant Lambda log groups and filter results to only entries that contain a specific request ID.

With Logs Insights, the developer can select both Lambda log groups, set a time range around the failure, and run a query such as filtering on the request ID field or matching the request ID string in the message. This provides a fast way to reconstruct the end-to-end flow and identify where the failure occurred—without writing any custom code, building data pipelines, or exporting logs.

Option A (using an AWS SDK) requires writing and maintaining code to call CloudWatch Logs APIs, handle pagination, time windows, filtering, and correlation across groups—more effort than necessary. Option B (export to S3 + Athena) adds significant setup (export tasks, S3 storage, Athena tables/partitions) and is better suited to large-scale analytics or long-term archival, not quick troubleshooting. Option D (Live Tail) is primarily for real-time streaming of new log events; it is less suitable for retrospective investigation of an incident that already happened, and it doesn’t provide the same structured querying and cross-log-group correlation capabilities as Logs Insights.

Therefore, CloudWatch Logs Insights (C) is the most direct, AWS-native, low-effort solution to query both Lambda log groups and filter by request IDs to troubleshoot the failing process flow.

Comprehensive Detailed Step by Step Explanation with All AWS Developer References:

In this scenario, the developer is configuring a mock integration in API Gateway. The integration request mapping template allows you to map the incoming request data to a format that the API expects. For mock integration, it ' s common to return specific HTTP status codes based on the conditions.

Using $context.integration.status: The $context.integration.status variable refers to the status of the API Gateway integration, which is useful for generating responses based on the condition. Option D correctly uses this variable to determine the HTTP status code, returning 200 for a successful mock request or 500 for a failure.

Alternatives:

Options A, B, and C do not use the correct context variables for handling mock integrations. These options would not return the correct status codes based on the actual integration status.

API Gateway Mapping Templates and Accessing Context Variables