DVA-C02 Development with AWS Services Practice Test 19 — 15 Questions

Question 1

A developer is implementing an e-commerce application where a purchase operation must deduct inventory and create an order atomically. The inventory and orders are stored in separate DynamoDB tables. Which DynamoDB feature should the developer use to execute these operations as a single, all-or-nothing transaction?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

DynamoDB Transactions. DynamoDB Transactions provide ACID (Atomicity, Consistency, Isolation, Durability) guarantees across one or more tables within a single AWS account and region. This allows the developer to combine the deduct-inventory and create-order operations into a single all-or-nothing transaction, ensuring that both succeed or both fail without partial updates.

Answer

DynamoDB Streams

Answer

DynamoDB Accelerator (DAX)

Answer

DynamoDB Global Tables

Question 2

A developer is building a serverless application using AWS Lambda and Amazon API Gateway. The API requires that the same Lambda function handle different HTTP methods (GET, POST, DELETE) for the same resource. The developer wants to minimize code and configuration. Which integration type should the developer use?

Accepted Answer

Lambda proxy integration. Lambda proxy integration (option A) is correct because it automatically passes the entire HTTP request (method, headers, query parameters, path parameters) to the Lambda function as a single event object, allowing the same function to inspect the `httpMethod` field and branch logic for GET, POST, DELETE without any additional API Gateway mapping or transformation configuration. This minimizes both code (the function handles routing internally) and configuration (no need to define separate integration requests/responses per method).

Answer

Lambda custom integration

Answer

HTTP integration

Answer

Mock integration

Question 3

An application running on Amazon EC2 instances behind an Application Load Balancer (ALB) intermittently returns 503 errors. The ALB health checks are failing for some instances intermittently. The developer checks the instance system logs and finds no application errors. What is the most likely cause of the health check failures?

Accepted Answer

The application on the instances is experiencing resource exhaustion (e.g., memory or CPU) which causes it to stop responding to health checks temporarily. Intermittent 503 errors from the ALB combined with intermittent health check failures and no application errors in the system logs strongly point to transient resource exhaustion (CPU or memory) on the EC2 instances. When an instance runs out of memory or CPU, the application process may become unresponsive or be killed by the OS (e.g., OOM killer), causing it to fail health checks temporarily. Once resources are freed (e.g., after a spike subsides), the application resumes responding, which explains the intermittent nature of the failures.

Answer

The security group for the instances does not allow inbound traffic from the ALB on the health check port

Answer

The health check path is not configured correctly and the default path returns a 404 status

Answer

The target group is not configured with the correct protocol

Question 4

A company is building a RESTful API using Amazon API Gateway and AWS Lambda. The API must allow users to authenticate using an identity provider that supports OpenID Connect (OIDC). The developer wants to offload authentication and authorization to API Gateway. Which API Gateway feature should the developer use?

Accepted Answer

Native JWT authorizer (HTTP API). The Native JWT authorizer for HTTP APIs in API Gateway directly validates JSON Web Tokens (JWTs) from an OIDC-compliant identity provider without requiring custom code. This offloads both authentication and authorization to API Gateway by configuring the issuer URL and audience, matching the requirement to use an OIDC provider.

Answer

Amazon Cognito User Pools authorizer

Answer

Custom Lambda authorizer

Answer

AWS IAM authorizer

Question 5

A developer is creating a REST API using Amazon API Gateway with Lambda proxy integration. The API needs to accept and return binary data such as images or PDF files. The developer has configured the API to use the Lambda proxy integration. What additional configuration is required to support binary data?

Accepted Answer

In API Gateway, add the binary media types to the API settings, e.g., image/png, application/pdf.. With Lambda proxy integration, API Gateway passes the client request as-is to Lambda and returns the Lambda response as-is to the client. To handle binary data, you must explicitly declare the binary media types (e.g., image/png, application/pdf) in the API Gateway REST API settings. This tells API Gateway to base64-encode the binary payload before sending it to Lambda and to decode the base64-encoded response from Lambda back to binary for the client. Without this configuration, API Gateway treats all payloads as text and will corrupt binary data.

Answer

Set the Content-Type header to application/octet-stream in the Lambda response.

Answer

Use an API Gateway custom domain with an SSL certificate.

Answer

Enable API caching with binary support.

Question 6

A developer is building a REST API using Amazon API Gateway that will serve static content from an Amazon S3 bucket. The API should cache responses for frequently accessed objects to reduce latency. Which API Gateway feature should the developer enable?

Accepted Answer

API Gateway caching with TTL set per method.. API Gateway caching allows you to cache responses from your backend (e.g., an S3 bucket) for a specified Time-to-Live (TTL) per method, reducing the number of calls to the backend and lowering latency for frequently accessed objects. This feature is natively integrated with API Gateway and requires no additional services or complex configurations, making it the most direct solution for caching static content served through a REST API.

Answer

Amazon CloudFront as a custom domain.

Answer

Lambda@Edge for caching.

Answer

S3 Transfer Acceleration.

Question 7

A developer is building a serverless application using AWS SAM. The application includes a Lambda function that needs read-only access to an S3 bucket. The developer wants to use SAM's built-in policy templates to grant this permission. Which policy template should be used in the SAM template?

Accepted Answer

S3ReadPolicy. The S3ReadPolicy template is the correct choice because it grants read-only access to an S3 bucket, which aligns with the requirement for the Lambda function. AWS SAM provides this built-in IAM policy template to simplify attaching least-privilege permissions, specifically allowing s3:GetObject, s3:ListBucket, and similar read operations.

Answer

S3CrudPolicy

Answer

S3FullAccessPolicy

Answer

S3StreamPolicy

Question 8

A developer is building a REST API using Amazon API Gateway and AWS Lambda. The API must support request validation, request throttling, and API keys. Which API Gateway feature should the developer use to enforce a daily request limit for each API key?

Accepted Answer

Usage plans. Usage plans in API Gateway allow you to set throttling and quota limits per API key, enabling daily request limits for each key. This feature is specifically designed to control usage by associating API keys with a plan that defines rate limits and quotas, such as a daily request cap. Option A is correct because it directly addresses the requirement to enforce a daily request limit per API key.

Answer

API keys

Answer

Throttling settings at the method level

Answer

AWS WAF

Question 9

A developer is creating a REST API using Amazon API Gateway and multiple AWS Lambda functions for different endpoints. The API must support CORS for a web application hosted on a different domain. The developer is using Lambda proxy integration. Which configuration is required to enable CORS?

Accepted Answer

Enable CORS in API Gateway and configure the Lambda functions to return the required CORS headers.. With Lambda proxy integration in API Gateway, the entire request and response are passed through to the Lambda function, which must return the HTTP response including status code, headers, and body. To enable CORS, the Lambda function must include the required CORS headers (e.g., Access-Control-Allow-Origin) in its response. While API Gateway can be configured to add CORS headers for non-proxy integrations, with proxy integration the Lambda function is solely responsible for returning all headers.

Answer

Configure API Gateway to return CORS headers and Lambda functions can ignore CORS.

Answer

Configure Lambda functions to return CORS headers and API Gateway will pass them through automatically.

Answer

Use a Lambda@Edge function at Amazon CloudFront to add CORS headers.

Question 10

A developer is building a microservices application composed of multiple AWS Lambda functions and an Amazon API Gateway. The developer needs to trace requests as they travel through different services to identify performance bottlenecks. Which AWS service should the developer integrate?

Accepted Answer

AWS X-Ray. AWS X-Ray is the correct service because it provides end-to-end tracing of requests as they travel through distributed applications, including AWS Lambda functions and API Gateway. It generates a service map that shows the flow of requests, latency breakdowns, and identifies performance bottlenecks across microservices. X-Ray integrates directly with Lambda and API Gateway via the X-Ray SDK and tracing headers, enabling trace propagation without code changes.

Answer

AWS CloudTrail

Answer

Amazon CloudWatch Logs

Answer

Amazon Inspector

Question 11

A developer is building a serverless web application using AWS Lambda and Amazon DynamoDB. The application needs to perform complex aggregations on data stored in DynamoDB. Which AWS service should the developer use to perform these aggregations efficiently without reading all the data into Lambda?

Accepted Answer

DynamoDB Streams with AWS Lambda. DynamoDB Streams captures item-level changes in near real-time and can trigger a Lambda function to perform incremental aggregations without scanning the entire table. This pattern avoids reading all data into Lambda, making it efficient for continuous aggregation workloads.

Answer

AWS Glue

Answer

Amazon EMR

Answer

Amazon Redshift

Question 12

A developer is building a serverless API using Amazon API Gateway and AWS Lambda. The API accepts JSON payloads in the request body. The developer wants to ensure that incoming requests have a valid structure before being passed to the Lambda function to reduce unnecessary invocations. Which API Gateway feature should the developer use?

Accepted Answer

Request validation using models and request validators. API Gateway's request validation feature allows you to define a JSON Schema model for the request body and attach a request validator to the method. This validates the payload structure before the request reaches the Lambda function, preventing invalid payloads from triggering unnecessary invocations and reducing costs.

Answer

Usage plans with API keys

Answer

WAF (AWS WAF) integration

Answer

Custom authorizer (Lambda authorizer)

Question 13

A developer is building a RESTful API using Amazon API Gateway. The API experiences high traffic spikes, and many requests are for the same data (e.g., a product catalog). The developer wants to reduce the load on the backend Lambda functions and improve response times for repeated requests. Which feature should the developer enable?

Accepted Answer

Enable API Gateway caching and set a TTL.. API Gateway caching stores responses from backend Lambda functions for a configurable time-to-live (TTL). When a request for the same data (e.g., a product catalog) arrives within the TTL period, API Gateway serves the cached response directly, reducing the number of invocations to the Lambda function and improving response latency. This directly addresses the need to reduce load on the backend and improve response times for repeated requests.

Answer

Use CloudFront with the API Gateway as an origin.

Answer

Enable throttling on the API Gateway usage plan.

Answer

Use a DynamoDB Accelerator (DAX) cluster for the backend database.

Question 14

A developer is building a REST API using Amazon API Gateway and wants to transform the request data before sending it to the backend Lambda function. The transformation includes mapping query string parameters to a JSON body. Which API Gateway feature should be used?

Accepted Answer

Velocity Template Language (VTL) mapping templates. API Gateway uses Velocity Template Language (VTL) mapping templates to transform incoming request data, such as mapping query string parameters into a JSON body before passing it to the backend Lambda function. This feature allows you to define a template that extracts values from the request's query string parameters (e.g., `$input.params('paramName')`) and constructs a new JSON payload, enabling seamless integration with Lambda without modifying the client request.

Answer

Lambda authorizer

Answer

Request validator

Answer

CORS configuration

Question 15

A developer is building a RESTful API using Amazon API Gateway and Lambda. The API should support CORS for a specific origin (https://example.com) and allow only GET and POST methods. Which configuration in the OPTIONS method response will satisfy these requirements?

Accepted Answer

Access-Control-Allow-Origin: https://example.com, Access-Control-Allow-Methods: GET,POST. The OPTIONS method response must include the `Access-Control-Allow-Origin` header set to the specific origin `https://example.com` to restrict CORS access, and the `Access-Control-Allow-Methods` header must list only the allowed HTTP methods (`GET,POST`). The OPTIONS method itself is a preflight request and does not need to be listed in the allowed methods; it is automatically handled by the browser. This configuration satisfies the requirement of supporting CORS for a single origin and only GET and POST methods.

Answer

Access-Control-Allow-Origin: *, Access-Control-Allow-Methods: GET,POST,OPTIONS

Answer

Access-Control-Allow-Origin: https://example.com, Access-Control-Allow-Methods: GET,POST,OPTIONS

Answer

Access-Control-Allow-Origin: https://example.com, Access-Control-Allow-Headers: Content-Type