DVA-C02 Development with AWS Services Practice Question
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?
⚠ Common exam trap
Test-takers frequently assume Lambda proxy integration automatically handles binary data because it passes everything through, but in reality, API Gateway requires explicit binary media type configuration to avoid corrupting binary payloads during base64 encoding/decoding.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
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 analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Set the Content-Type header to application/octet-stream in the Lambda response.
Why it's wrong here
While setting the Content-Type header in the Lambda response is a crucial step to inform the client about the data type, it is insufficient on its own for API Gateway to correctly handle binary data. Without explicit configuration in API Gateway to recognize `application/octet-stream` as a binary media type, API Gateway will treat the Lambda response body as a UTF-8 string. This often results in the binary data being incorrectly base64-encoded or corrupted during transit, preventing proper rendering by the client.
- ✓
In API Gateway, add the binary media types to the API settings, e.g., image/png, application/pdf.
Why this is correct
This is the correct and essential step for API Gateway to properly handle binary data from a Lambda integration. By explicitly listing media types like `image/png` or `application/pdf` in the API Gateway's binary media types settings, you instruct API Gateway to treat incoming and outgoing payloads of these types as raw binary data. This ensures that API Gateway correctly base64-encodes binary responses from Lambda before sending them to the client and decodes binary requests before passing them to Lambda, preventing data corruption.
- ✗
Use an API Gateway custom domain with an SSL certificate.
Why it's wrong here
Using an API Gateway custom domain with an SSL certificate enhances the API's branding and provides secure, encrypted communication (HTTPS) between clients and the API Gateway endpoint. While crucial for production APIs, this configuration is entirely unrelated to how API Gateway processes or transmits binary data payloads. It addresses the API's public URL and transport-level security, not the content type handling mechanism.
- ✗
Enable API caching with binary support.
Why it's wrong here
Enabling API caching is designed to improve API performance and reduce the load on backend integrations by storing responses for subsequent identical requests. While API Gateway caching can indeed store binary responses once they are correctly configured and processed as binary, the caching mechanism itself does not enable or configure the fundamental ability for API Gateway to recognize and handle binary media types. Binary support must be established independently through the API's settings.
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
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