DVA-C02 Development with AWS Services Practice Question
This DVA-C02 practice question tests your understanding of development with aws services. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A development team is building a real-time chat application using Amazon API Gateway WebSocket APIs and AWS Lambda. The application needs to maintain a connection to each user and broadcast messages to all connected clients. Which approach should the developer use to scale the application efficiently?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Store connection IDs in Amazon DynamoDB and use the API Gateway Management API to send messages to all connections.
API Gateway WebSocket APIs maintain persistent connections. When a client sends a message, API Gateway invokes a Lambda function. To broadcast to all connected clients, the Lambda function needs to call the API Gateway Management API to send messages to each connection. The connection IDs must be stored in a shared data store like DynamoDB. The other options are not suitable: SQS is for message queuing, not broadcasting; SNS is pub/sub but doesn't integrate directly with WebSocket connections; ElastiCache is not designed for this use case.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Store connection IDs in Amazon DynamoDB and use the API Gateway Management API to send messages to all connections.
Why this is correct
DynamoDB stores connection IDs, and the Management API sends messages to each connection.
Use Amazon ElastiCache to cache connection IDs and have Lambda send messages using the Redis pub/sub feature.
Why it's wrong here
ElastiCache Redis pub/sub is for in-memory messaging, not for sending messages through API Gateway.
✗
Use Amazon SNS to publish messages to all connected clients via the WebSocket API.
Why it's wrong here
SNS does not natively support WebSocket endpoints.
✗
Use Amazon SQS to queue messages and have Lambda poll the queue to send messages to all connections.
Why it's wrong here
SQS is not designed for broadcasting to WebSocket connections.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related DVA-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Development with AWS Services — This question tests Development with AWS Services — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Store connection IDs in Amazon DynamoDB and use the API Gateway Management API to send messages to all connections. — API Gateway WebSocket APIs maintain persistent connections. When a client sends a message, API Gateway invokes a Lambda function. To broadcast to all connected clients, the Lambda function needs to call the API Gateway Management API to send messages to each connection. The connection IDs must be stored in a shared data store like DynamoDB. The other options are not suitable: SQS is for message queuing, not broadcasting; SNS is pub/sub but doesn't integrate directly with WebSocket connections; ElastiCache is not designed for this use case.
What should I do if I get this DVA-C02 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related DVA-C02 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Question Discussion
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