Why DynamoDB pairs with Lambda - Challenge Your Understanding

Challenge - 5 Problems

🧠 Conceptual

intermediate

Why is DynamoDB a good match for AWS Lambda?

Which reason best explains why DynamoDB works well with AWS Lambda?

A Lambda functions can only read data from DynamoDB but cannot write back to it.

B DynamoDB stores data in files that Lambda reads directly from the file system.

C DynamoDB requires manual polling by Lambda to detect data changes, which is efficient.

D DynamoDB automatically triggers Lambda functions on data changes, enabling event-driven processing.

💡 Hint

Think about how Lambda can react to changes in DynamoDB data automatically.

DynamoDB Streams can trigger Lambda functions automatically when data changes, making it easy to build event-driven applications.

🧠 Conceptual

intermediate

What benefit does Lambda provide when paired with DynamoDB?

What is a key benefit of using Lambda with DynamoDB for backend logic?

A Lambda lets you run backend code without managing servers, triggered by DynamoDB events.

B Lambda requires you to manage servers to process DynamoDB data.

C Lambda only works with relational databases, not DynamoDB.

D Lambda stores data permanently, replacing DynamoDB's role.

💡 Hint

Consider how Lambda helps run code without worrying about servers.

Lambda is serverless, so it runs your code in response to DynamoDB events without you managing any servers.

❓ query_result

advanced

What output does this DynamoDB Stream event Lambda receive?

Given a DynamoDB table with an item inserted, what does the Lambda event contain?

DynamoDB

Event example: { "Records": [ { "eventName": "INSERT", "dynamodb": { "NewImage": { "id": { "S": "123" }, "name": { "S": "Alice" } } } } ] }

A The event is empty because inserts do not trigger Lambda.

B The event contains only the old item data before insertion.

C The event contains the new item data under Records[0].dynamodb.NewImage.

D The event contains a SQL query string to fetch the new item.

💡 Hint

Think about what data DynamoDB Streams send on an insert.

On an insert, DynamoDB Streams send the new item data in NewImage, which Lambda receives in the event.

❓ optimization

advanced

How to optimize Lambda processing with DynamoDB Streams?

Which approach best optimizes Lambda function performance when processing DynamoDB Streams?

A Disable DynamoDB Streams to avoid Lambda triggers and improve speed.

B Batch multiple stream records in one Lambda invocation to reduce overhead.

C Invoke a separate Lambda for each individual stream record immediately.

D Use Lambda to poll DynamoDB table every second instead of streams.

💡 Hint

Think about reducing the number of Lambda invocations for efficiency.

Batching multiple stream records in one Lambda invocation reduces cold starts and overhead, improving performance.

🔧 Debug

expert

Why does this Lambda fail to process DynamoDB Stream events?

Given this Lambda code snippet processing DynamoDB Stream events, why does it fail?

exports.handler = async (event) => {
  const record = event.Records[0];
  const id = record.dynamodb.NewImage.id;
  console.log('ID:', id);
};

A Because NewImage attributes are objects with type keys, you must access id.S to get the string value.

B Because event.Records is empty on insert events, so record is undefined.

C Because Lambda cannot access DynamoDB Stream events without special permissions.

D Because console.log is not supported in Lambda functions.

💡 Hint

Remember how DynamoDB represents attribute values in streams.

DynamoDB Stream records represent attribute values as objects with type keys like S for string, so you must use id.S to get the actual value.