AWS Lambda

• You can 1($) without provisioning or maintaining servers.
• It 2($) for you in response to events.
• It 3($) automatically.
• It provides built-in code 4($) via Amazon CloudWatch.

An 1($) architecture uses events to initiate actions and communication between decoupled services.

• When an invocation is routed to a new execution environment, Lambda must initialize the environment, download the code, initialize the runtime, and any packages or dependencies required by your function.  This is the 1($) latency.
• When an invocation gets routed to an environment that is already available for the function, it gets a 2($) and Lambda only needs to run the code.

• 1($) - An entry point that AWS Lambda calls to initiate your Lambda function.
• 2($) - An object with information about the event that initiated the Lambda function.
• 3($) - This is generated by AWS and provides metadata about the action

• 1($) - Like a house blueprint - you can threat infrastructure as code
• 2($) - Streamlined CloudFormation Template for serverless applications
• 3($) - Tool for local testing and debugging of serverless applications
• 4($) - AWS SAM CLI command for deploying AWS SAM template

Lambda is integrated with AWS CodeDeploy for automated rollout with traffic shifting. CodeDeploy supports multiple traffic shifting methods, in addition to alarms and hooks. CodeDeploy supports the following traffic-shifting patterns:

• 1($) – Traffic is shifted in two increments. If the first increment is successful, the second is completed based on the time specified in the deployment. 
• 2($) – With linear traffic shifting, traffic is slowly shifted in a predetermined percentage every X minutes based on how you have it configured. 
• 3($) – Shifts all traffic from the original Lambda function to the updated Lambda function version at once.

• 1($) – These instruct CloudWatch to monitor the deployment and trigger an alarm if any errors occurred during rollout. Any alarms would automatically roll back your deployment. 
• 2($) – Give you the option to run pre-traffic and post-traffic test functions that run sanity checks before traffic-shifting starts to the new version and after traffic-shifting completes. 

• 1($) - The number of times your function code is run, including successful runs and runs that result in a function error.
• 2($) - The amount of time that your function code spends processing an event.
• 3($) - The number of invocations that result in a function error. Function errors include exceptions thrown by your code and exceptions thrown by the Lambda runtime.
• 4($) - The number of times that a process failed because of concurrency limits. 
• 5($) - Pertains to event source mappings that read from streams. The age of the last record in the event. The age is the amount of time between when the stream receives the record and when the event source mapping sends the event to the function.
• 6($) - For asynchronous invocation, this is the number of times Lambda attempts to send an event to a dead-letter queue but fails. 
• 7($) - The number of function instances that are processing events.