Lambda

Question 1

Lambda pricing

Answer 1

pay per request and compute time

Question 2

how to improve lambda performance

Answer 2

increasing RAM of function improves cpu and network

Question 3

Lambda use cases

Answer 3

• serverless cron
• thumbnail creation

Question 4

lambda with ALB

Answer 4

• put lambda into target group. in alb, http converted into JSON
  
  • multi header values - alb setting that sends query string parameters and headers as an array to lambda

Question 5

Asynchronous lambda

Answer 5

• events sent to event queue
  
  • s3, sns, cloudwatch event bridge
• 2 retries = 3 tries total max
• **should be idempotent - if task is retried, the result should be the same
• can create DLQ for failed tasks

Question 6

cloudwatch event bridge w/ lambda

Answer 6

• can create a cron job or codepipeline eventbridge rule
• resource based policy allows access

Question 7

lambda Event Source Mapping

Answer 7

• sync
• requires an execution role to be created to read from other aws services
  
  • best practice - create one execution role per function
  • lambda has an execution role to read from other services

Question 8

lambda destinations

Answer 8

• dlq that includes failures AND successes
  
  • async invocations - define destination for successful or failed event
    
    • sqs, sns, lambda, eventbridge bus
    • AWS recommends aws destinations instead of DLQ now
  • event source mapping - send discarded event batches to destination
    
    • sqs, sns

Question 9

lambda tracing

Answer 9

Question 10

lambda networking

Answer 10

• by default, lambda is outside your vpc so it can’t access vpc resources like internal ELB, elasticache, etc.
• to deploy lambda in vpc - define vpc id, subnets, and security groups
  
  • lambda will create an ENI - elastic network interface
  • requires lambda vpc access execution role
• lambda in a public subnet does NOT have internet access or public IP
  
  • use a NAT gateway / instance with lambda deployed in private subnet to give it pub access

Question 11

lambda configurations

Answer 11

• add more ram to get mroe vCPU credits
• timeout - default 3 seconds, max 15 minutes
  
  • more than 15 minutes? use ecs, fargate, or ec2

Question 12

lambda concurrency

Answer 12

• reserved concurrency
  
  • up to 50concurrent executions for all lambdas in your account
• can set ‘reserved concurrency’ to set limit for when to throttle
• throttle error
  
  • sync invocation - throttle error 429
  • async - retry automatically then go to DLQ
• cold start - cold is loaded and initialization time
• provisioned concurrency - concurrency is allocated in advance
  
  • keep function warm - no cold start

Question 13

testing lambda containers locally

Answer 13

test the containers locally using the Lambda Runtime Interface Emulator.

Question 14

lambda container uploaded to ECR

Answer 14

must be in the same account as (ECR and where you created the lambda)

Question 15

Improve lambda latency stability

Answer 15

enable your function to scale without fluctuations in latency, use provisioned concurrency

Question 16

lambda reserved concurrency

Answer 16

To ensure that a function can always reach a certain level of concurrency, you can configure the function with reserved concurrency. When a function has reserved concurrency, no other function can use that concurrency. More importantly, reserved concurrency also limits the maximum concurrency for the function, and applies to the function as a whole, including versions and aliases.

You cannot configure Application Auto Scaling to manage Lambda reserved concurrency on a schedule.

Question 17

lambda layers

Answer 17

You can configure your Lambda function to pull in additional code and content in the form of layers. A layer is a ZIP archive that contains libraries, a custom runtime, or other dependencies