Serverless - Lambda

Question 1

What is AWS Lambda?

Answer 1

AWS Lambda is a serverless compute service that runs your code in response to events and automatically manages the compute resources.

Question 2

What is the maximum execution time for a Lambda function?

Answer 2

15 minutes per invocation.

Question 3

How does Lambda scale?

Answer 3

Lambda automatically scales by running code in parallel in response to incoming requests or events.

Question 4

Why is Lambda considered cost-effective?

Answer 4

You only pay for the compute time and requests, and it offers a generous free tier.

Question 5

How can you limit the number of concurrent executions for a Lambda function?

Answer 5

By setting a reserved concurrency limit at the function level.

Question 6

What happens if a Lambda function exceeds its reserved concurrency limit?

Answer 6

Invocations beyond the limit are throttled.

Question 7

What is the default account-wide concurrency limit for Lambda functions?

Answer 7

1,000 concurrent executions per region.

Question 8

Can the account-wide concurrency limit be increased?

Answer 8

Yes, by submitting a support request to AWS.

Question 9

What is provisioned concurrency in Lambda?

Answer 9

It pre-allocates instances of a Lambda function to avoid cold starts and reduce latency.

Question 10

What is Lambda SnapStart?

Answer 10

It improves your Lambda functions performance up to 10x at no extra cost for Java 11 and above by invoking it from a pre-initialised state.

Question 11

What are the two types of Edge Functions provided by AWS?

Answer 11

CloudFront Functions and Lambda@Edge.

Question 12

What are CloudFront Functions used for?

Answer 12

High-scale, latency-sensitive customizations for viewer requests and viewer responses.

Question 13

What events can Lambda@Edge modify?

Answer 13

Viewer request
Viewer response
Origin request
Origin response

Question 14

Where are Lambda functions launched by default?

Answer 14

In an AWS-managed VPC, outside of the user’s VPC.

Question 15

Can a default Lambda function access private resources in your VPC?

Answer 15

No, it cannot access private resources like RDS, ElastiCache, or internal load balancers.

Question 16

What problem arises when Lambda functions access RDS directly under high load?

Answer 16

Too many open connections can cause timeouts and database issues.

Question 17

What are the three benefits of using an RDS proxy with Lambda?

Answer 17

Improved scalability: By pooling and sharing database connections.
Improved availability: Reduces failover time by 66% and preserves connections.
Enhanced security: Enforces IAM authentication and integrates with AWS Secrets Manager.

Question 18

Why must Lambda functions be in the same VPC as the RDS proxy?

Answer 18

The RDS proxy is private and not publicly accessible, so Lambda must be in the VPC for network connectivity.

Question 19

What service helps Lambda handle database connections more efficiently in a VPC?

Answer 19

RDS Proxy.

Question 20

What is an example use case for direct Lambda invocation from a database?

Answer 20

A user inserts data into a table (e.g., a registration table), and the database invokes a Lambda function to send a welcome email.

Question 21

Which databases support invoking Lambda functions directly?

Answer 21

RDS for PostgreSQL
Aurora MySQL