Lambda Exam Tips (dev)

Lambda triggers: be aware of the services that can trigger a lambda function
Serverless Technology: Lambda, API Gateway, DynamoDB, S3, SNS, SQS
Independent: Lambda functions are independent, each event will trigger a single function
Extremely Cost Effective: Pay only when your code executes
Continuous Scaling: Lambda scales automatically
Event-Driven: Lambda functions are triggered by an event of action

Versioning

$LATEST tag refers to the latest uploaded Lambda code
You can use versioning an aliasing to point your applications to specific version if you don't want to use $LATEST
If you use alias instead of $LATEST, it will not use the lastest code automatically
If no alias is specific at the end of the ARN, then it will use $LATEST
ARN example
- arn:aws:lambda:us-west-2:123456789012:function:my-function:Prod
- arn:aws:lambda:us-west-2:123456789012:function:my-function:$LATEST

The limit is of 1,000 concurrent executions per second
It's likely that you hit the limit at some point
If you hit the limit you'll see a 429 HTTP response
You can get the limit raised by the AWS support
Reserved concurrency guarantees that a set number of concurrent executions are always available for critical functions

It's possible to enable the Lambda to access resources that are under a private VPC
In order to access a private VPC, it needs VPC ID, private subnet ID, security group ID
Lambda create ENIs (Elastic Network Instance) using IPs from the private subnets
The security group allows your function to access resources under the VPC

	`/tmp` Ephemeral Storage	Lambda Layer	S3 (external)	EFS (external)
Use Case:	`Temporary` data	`Libraries` and `SDKs`	`Persistent` data	`Persistent` data
Size Limit:	512 MB - 10 GB	50 MB zipped - 250 MB zipped	Elastic	Elastic
Dynamic Updates:	`Dynamic` read/write	Updates require a `new` layer	`Store` and `retrieve`	`Dynamic` read/write
Shared:	Shared `within` the EE	Shared `accross` EEs	Shared `accross` EEs	Shared `accross` EEs

EE = Execution Environment

The deployment package is created by default is you use the console
Deployment packages that are larger the 50 MB in size must be zipped and uploaded to S3
You can use Lambda Layer is best practice to reduce the size of the deployment package

Increase the memory can reduce the execution time
Importing library can slow down the initialization of your function
Only import what you need to use (es. import aws-cdk/clients/dynamodb instead of aws-cdk)