Lambda

Question 1

How would you set up a serverless CRON job using Lambda?

Answer 1

Create an EventBridge rule to trigger a Lambda function periodically

Question 2

Using an ALB with Lambda how would you enable multi header values?

Answer 2

Enable the multi value setting on the ALB target group, the header values would then be available as an array

Question 3

What is Event Source Mapping in Lambda?

Answer 3

Enables polling of messages from either Kinesis data streams or an SQS queue to be processed by lambda in batches

Question 4

What determines the order in which items from a kinesis data stream are processed using a lambda event mapping?

Answer 4

In order at the shard level

Question 5

What happens if your lambda function returns an error when processing a batch from a kensis data stream?

Answer 5

By default the entire batch is reprocessed until the function succeeds or the items in the batch expire

Question 6

How does lambda scale when processing a FIFO SQS queue?

Answer 6

Scales up to the number of active message groups (GroupID)

Question 7

How does lambda scale when processing a standard SQS queue?

Answer 7

Scales up to process as fast as possible

Question 8

When using lambda to process batches from a Kinesis data stream configured for parallelisation how many batches can be processed per shard at the same time?

Answer 8

10 batches

Question 9

What are the main differences between CloudFront Functions and Lambda@Edge?

Answer 9

• Runtime support - JavaScript only for CF Functions, Node & Python for Lambda
• CloudFront can handle more requests per second
• CloudFront Functions triggered by viewer request/response, Lambda can be triggered also by origin request/response

Question 10

Would a Lambda function deployed in a private VPC have internet access by default?

Answer 10

No

Question 11

How can you give internet access to a Lambda function deployed in a private VPC?

Answer 11

Deploy a NAT gateway in a public VPC

Question 12

How can a Lambda function deployed in a private VPC access AWS serverless services?

Answer 12

Use a VPC endpoint to privately access AWS services, you could also use a NAT gateway in a public VPC

Question 13

What is one way you can improve the performance of a Lambda function by changing a setting?

Answer 13

Increase RAM - CPU increases with RAM, you can’t directly increase CPU

Question 14

What is the Lambda execution context?

Answer 14

A space where external libaries can be loaded, it can be shared between invokations. For example a database connection can be setup outside of the handler function.

Question 15

What are Lambda Layers?

Answer 15

Custom runtimes for Lambda e.g. C++ and other dependencies, can be shared between Lambda functions

Question 16

Can Lambda mount an EFS file system?

Answer 16

Yes, as long as the Lambda is running in a VPC, uses an EFS Access Point (path)

Question 17

What is the maximum memory allocation available for Lambda?

Answer 17

10Gb

Question 18

What is the maximum execution time for Lambda?

Answer 18

15mins

Question 19

What is the disk capacity in the Lambda function container (/tmp)?

Answer 19

10Gb

Question 20

What is the maximum number of concurrent Lambda executions?

Answer 20

1000

Question 21

You have enabled a Dead Letter Queue (DLQ) for your Lambda function and configured it to send failed messages to SNS. While testing, you don’t see any events there even though you can tell from CloudWatch metrics that you have failures. What is most likely the reason for this?
1. You should use SQS instead as there is no Lambda DLQ for SNS
2. Your Lambda function is missing permissions

Answer 21

2. Your Lambda function is missing permissions

Question 22

Which of the following AWS service does NOT require a Lambda Event Source Mapping?
1. DynamoDB Streams
2. Kinesis Data Streams
3. SQS
4. SNS

Answer 22

4. SNS (because it is asyncronous)