Serverless Summary

Lambda - Exam Tips

Lambda scales out (not up) automatically
- You can have many concurrent lambda functions running at once
Lambda functions are independent, 1 event = 1 function
Lambda is serverless
Know which services are serverless!
- S3
- DynamoDB
Lambda functions can trigger other lambda functions, 1 event can = x functions if functions trigger other functions
Architectures can get extremely complicated, AWS X-Ray allows you to debug what is happening
- updates to DB, SNS notifications failing
Lambda can do things globally, you can use it to back up S3 buckets to other S3 buckets etc
Know the lambda triggers

Remember what API gateway is at a high level
- restaurant
- Customer submits request to Waiter, Waiter takes requests, sends to kitchen
API Gateway has caching capabilities to increase performance
- McDonalds keeps big macs and burgers already made (cached)
- If you order a salad or fish sandwich, they would actually have to make it (not cached)
API Gateway is low cost and scales automatically
You can throttle API Gateway to prevent attacks
You can log results to CloudWatch
If you are using JavaScript/AJAX that uses multiple domains with API Gateway, ensure that you have enabled CORS on API Gateway
CORS is enforced by the client

Can have multiple versions of lambda functions
latest version will use $latest
qualified version will use $latest, unqualified will not have it
versions are immutable (cannot be changed)
Can split traffic using aliases to different versions
- Cannot split traffic with $latest, instead create an alias to latest

Great way to visualize your serverless application
Step functions automatically triggers and tracks each step
Step functions logs the state of each step so if something goes wrong you can track what went wrong and where

The X-Ray SDK Provides:

Interceptors to add to your code to trace incoming HTTP requests
Client handlers to instrument AWS SDK clients that your application uses to call other AWS services
An HTTP client to use to instrument calls to other internal and external HTTP web services

The X-Ray integrates with the following AWS services:

The X-Ray integrates with the following languages: