WebSocket (API Gateway WebSocket API) quiz · Level 0

Question 1When a todo changes, Todo.io wants every open browser tab to update at once, without the browser asking again and again. What fits?

An API Gateway WebSocket API; the backend pushes to each connection.Correct. A WebSocket stays open both ways, so the server can send whenever something happens.A REST API with a longer timeout.Not this one. The browser still has to ask; the server can only answer.An SQS queue the browser reads from.Not this one. Browsers don't read SQS queues, and that would still be asking repeatedly.CloudWatch Logs.Not this one. Logs are for engineers to read, not for talking to browsers.

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Question 2Which routes does every API Gateway WebSocket API have built in?

$connect, $disconnect and $default.Correct. They run when a browser connects, when it disconnects, and for any message no other route matches. Each can call Lambda or an HTTP backend.GET, POST, PUT and DELETE.Not this one. Those are HTTP methods, used by REST APIs./login and /logout.Not this one. Those would be routes you design yourself.$open, $close and $message.Not this one. The names are $connect, $disconnect and $default.

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Question 3Todo.io's Lambda function tries to push a message to a browser by POSTing to the WebSocket API's @connections URL, and gets AccessDenied. What fixes it?

Allow execute-api:ManageConnections in the function's execution role.Correct. Pushing to a connection is an AWS API call, so IAM must allow it like any other.Open port 443 in the function's security group.Not this one. AccessDenied is an IAM answer. A network problem would time out instead.Enable CORS on the API.Not this one. CORS is about browsers calling across websites. This call comes from Lambda.Give the browser an IAM role.Not this one. The browser is the receiver here, and app users are never IAM principals.

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Question 4Hundreds of browsers hold WebSocket connections open to Todo.io. How does the backend send a message to one of them?

By its connection id, which API Gateway gave that connection when it opened.Correct. The backend POSTs to @connections/{id}. Todo.io stores each user's connection ids when they connect.By the browser's IP address.Not this one. The backend never talks to browsers directly; API Gateway holds the connections.By the user's IAM ARN.Not this one. App users aren't IAM principals.By an SQS queue URL.Not this one. Queues aren't connected to browsers.

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Question 5What does "WebSocket (API Gateway WebSocket API)" mean?

An API Gateway API that keeps each browser connection open, so your backend can push messages at any time.Correct. Think of it as: An open phone line instead of sending letters back and forth.A managed HTTPS front door that passes requests to your code.Not this one. That describes API Gateway.Upload a function; AWS runs it only when something calls it.Not this one. That describes Lambda.Run containers on AWS. With Fargate, AWS also runs the servers underneath.Not this one. That describes ECS and Fargate.

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Question 6Which term is this? "An API Gateway API that keeps each browser connection open, so your backend can push messages at any time."

WebSocket (API Gateway WebSocket API)Correct. Yes. Think of it as: An open phone line instead of sending letters back and forth.API GatewayNot this one. API Gateway is: A managed HTTPS front door that passes requests to your code.LambdaNot this one. Lambda is: Upload a function; AWS runs it only when something calls it.ECS and FargateNot this one. ECS and Fargate is: Run containers on AWS. With Fargate, AWS also runs the servers underneath.

Learn it: WebSocket (API Gateway WebSocket API)

Question 7Which AWS term is described by this analogy? "An open phone line instead of sending letters back and forth."

WebSocket (API Gateway WebSocket API)Correct. Yes: An API Gateway API that keeps each browser connection open, so your backend can push messages at any time.API GatewayNot this one. API Gateway is: A managed HTTPS front door that passes requests to your code. Its analogy: A receptionist who takes every visitor's request and phones the right person.LambdaNot this one. Lambda is: Upload a function; AWS runs it only when something calls it. Its analogy: A taxi. You pay for the ride, not for owning the car.ECS and FargateNot this one. ECS and Fargate is: Run containers on AWS. With Fargate, AWS also runs the servers underneath. Its analogy: Handing over a packed lunchbox and letting someone else heat it up.

Learn it: WebSocket (API Gateway WebSocket API)

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