Lambda - Synchronous Invocations - Services

• User Invoked:
  • Elastic Load Balancing (Application Load Balancer)
  • Amazon API Gateway
  • Amazon CloudFront (Lambda@Edge)
  • Amazon S3 Batch
• Service Invoked:
  • Amazon Cognito
  • AWS Step Functions
• Other Services:
  • Amazon Lex
  • Amazon Alexa
  • Amazon Kinesis Data Firehose
• Error handling must happen client side (retries, exponential backoff, etc…)

Lambda – Asynchronous Invocations

• S3, SNS, CloudWatch Events…
• The events are placed in an Event Queue
• Lambda attempts to retry on errors
  • 3 tries total
  • 1 minute wait after 1st , then 2 minutes wait
• Make sure the processing is idempotent (in case of retries)
• If the function is retried, you will see duplicate logs entries in CloudWatch Logs
• Can define a DLQ (dead-letter queue) – SNS or SQS – for failed processing (need correct IAM permissions)
• Asynchronous invocations allow you to speed up the processing if you don’t need to wait for the result (ex: you need 1000 files processed)

Services that call asynchronous

• Amazon Simple Storage Service (S3)
• Amazon Simple Notification Service (SNS)
• Amazon CloudWatch Events / EventBridge
• AWS CodeCommit (CodeCommitTrigger: new branch, new tag, new push)
• AWS CodePipeline (invoke a Lambda function during the pipeline, Lambda must callback)

CloudFront Functions & Lambda@Edge