WTF is Lambda?

Lambda is an abstract compute service where all you need to do is upload your code… AWS manages the servers for you. Lambda works in an event driven, orchestration manner and as a result of a request via API gateway or an ALB.

Lambda functions can be called by specifying a version or alias (qualified ARN) OR without a version (unqualified ARN).

Serverless Application Model (SAM)

SAM is a CloudFormation extention optimized for serverless application. It’s basically macro library that enables serverless applications to use a more consise syntax for common patterns like functions, APIs, and tables.


With Amazon CloudFront, you can write your own code to customize how your CloudFront distributions process HTTP requests and responses instead of using CloudFront functions. Lambda@edge functions can be run when on viewer/origin request and on the viewer/origin response.

Interaction with other AWS services

  • SQS: max messages per batch = 10;

  • CloudWatch: can send matched event, part of the matched, or a constant chunk of JSON


  • function termination? out of memory

  • Synchronously call? (anything that requires a response to proceed)
    • ELB
    • Cognito
    • Lex
    • Alexa
    • API Gateway
    • CloudFront
    • Kinesis Firehouse
    • Step Functions
    • S3 Batch Functions
    • SQS
  • Asynchronously call? (anything that architecturally could be modeled as a queue)
    • S3
    • SNS
    • SES
    • CloudFormation
    • CloudWatch Logs & Events
    • AWS CodeCommit & CodePipeline
    • AWS Config
    • AWS IoT services
  • Process failed async innvocations? dead letter queue items with SQS or SNS

  • Configure number of retries? Sync = caller configured; async = twice

The old version of the function is served? there is a brief window of time, typically less than a minute, when the requests could be served by the older veersion.

Lambda to poll queue? Kinesis, DynamoDB (streams), SQS

Promote new version to LATEST? Update alias to new version (assuming you are following best practice by using an alias ARN)

Memory, timeout ranges? 128-10,240 MB, 900 seconds

Change permissions of Lambda? must use CLI/SDK; can’t use console

API Gateway

Integration sources? Lambda functions (in account or other account), Step Functions, HTTP endpoints (EB), EC2, non-AWS HTTP/S endpoints, or private end-points via VPC links/Direct Connect.

Caching using cache keys made from headers, query strings & URL; can set size and over-ride cached elements; when resized the cache is flushed.

Access control can be implemented using resource policies, IAM roles/policies, CORS, lambda authorizers, Cognito pools, SSL Certs, and usage plans.

Uses CloudWatch execution logging to capture user requests and response payloads.