- A
Store the WebSocket URL in the Lambda function environment variables.
Why wrong: The callback URL is derived from the API endpoint; the WebSocket URL is for client connections, not for server-side posting.
- B
Use the API Gateway callback URL to post messages to a specific connection.
The callback URL is in the format https://api-id.execute-api.region.amazonaws.com/@connections/{connectionId}.
- C
Grant the Lambda function IAM permission to execute the execute-api:ManageConnections action.
This permission allows the Lambda function to post messages to connected clients.
- D
Store the connection IDs in an Amazon DynamoDB table for later retrieval.
Why wrong: While storing connection IDs in DynamoDB is common, it's not required for the basic sending of messages; the callback URL is used directly.
- E
Extract the connection ID from the event object when a client connects.
The connection ID is provided in the event's requestContext.connectionId.
Broadcast Messages to All WebSocket Clients
This DVA-C02 practice question tests your understanding of development with aws services. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 developer is building a real-time chat application using Amazon API Gateway WebSocket APIs and AWS Lambda. The application needs to send messages to all connected clients. Which THREE actions are required to implement this functionality? (Choose THREE.)
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
Use the API Gateway callback URL to post messages to a specific connection.
Option B is correct because API Gateway WebSocket APIs provide a callback URL (the 'postToConnection' endpoint) that allows the backend to send messages to a specific connected client. The Lambda function must use this URL, combined with the connection ID, to post messages back through the WebSocket channel. Without this callback mechanism, the server cannot push messages to clients.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 the WebSocket URL in the Lambda function environment variables.
Why it's wrong here
The callback URL is derived from the API endpoint; the WebSocket URL is for client connections, not for server-side posting.
- ✓
Use the API Gateway callback URL to post messages to a specific connection.
Why this is correct
The callback URL is in the format https://api-id.execute-api.region.amazonaws.com/@connections/{connectionId}.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Grant the Lambda function IAM permission to execute the execute-api:ManageConnections action.
Why this is correct
This permission allows the Lambda function to post messages to connected clients.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Store the connection IDs in an Amazon DynamoDB table for later retrieval.
Why it's wrong here
While storing connection IDs in DynamoDB is common, it's not required for the basic sending of messages; the callback URL is used directly.
- ✓
Extract the connection ID from the event object when a client connects.
Why this is correct
The connection ID is provided in the event's requestContext.connectionId.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume storing connection IDs in a database (like DynamoDB) is mandatory for broadcasting, but the question asks for the three required actions, and DynamoDB is an optional optimization, not a core requirement for sending messages to all connected clients.
Detailed technical explanation
How to think about this question
Under the hood, the execute-api:ManageConnections IAM permission grants the Lambda function access to the @connections API, which uses the callback URL pattern: https://{api-id}.execute-api.{region}.amazonaws.com/{stage}/@connections/{connectionId}. The connection ID is extracted from the $connect route event's requestContext.connectionId, and the callback URL is constructed dynamically. In real-world scenarios, DynamoDB is often used to store connection IDs for broadcasting, but the question's three required actions are: granting IAM permissions (C), using the callback URL (B), and extracting the connection ID (E).
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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 |
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this DVA-C02 question test?
Development with AWS Services — This question tests Development with AWS Services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use the API Gateway callback URL to post messages to a specific connection. — Option B is correct because API Gateway WebSocket APIs provide a callback URL (the 'postToConnection' endpoint) that allows the backend to send messages to a specific connected client. The Lambda function must use this URL, combined with the connection ID, to post messages back through the WebSocket channel. Without this callback mechanism, the server cannot push messages to clients.
What should I do if I get this DVA-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
This DVA-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DVA-C02 exam.
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