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AWS Developer Associate Study Notes

AWS Lambda Core Concepts

Serverless compute service - the foundation of serverless development

Exam Domain

Development with AWS Services represents approximately 32% of the exam. Lambda is heavily tested.

Lambda Execution Model

Invocation Type	Behavior	Services	Error Handling
Synchronous	Caller waits for response	API Gateway, ALB, Cognito, Alexa	Caller handles errors
Asynchronous	Lambda queues event, returns 202	S3, SNS, EventBridge, SES	2 retries, then DLQ
Event Source Mapping	Lambda polls for records	Kinesis, DynamoDB Streams, SQS	Retry until success or record expires

Lambda Function Configuration

Setting	Description	Limits/Best Practices
Memory	128 MB to 10,240 MB	CPU scales proportionally with memory
Timeout	Maximum execution time	1 second to 15 minutes max
Ephemeral Storage	/tmp directory	512 MB to 10,240 MB
Environment Variables	Key-value configuration	4 KB total, use Secrets Manager for secrets
Reserved Concurrency	Limits concurrent executions	Protects downstream resources
Provisioned Concurrency	Pre-warmed execution environments	Eliminates cold starts, extra cost

Critical Lambda Limits

• Deployment Package: 50 MB zipped (direct upload), 250 MB unzipped

• Container Image: Up to 10 GB

• Concurrent Executions: 1,000 per region (soft limit)

• Invocation Payload: 6 MB (sync), 256 KB (async)

Lambda Execution Context

Cold Start: First invocation initializes execution environment (1-3 seconds)
Warm Start: Reuses existing environment (milliseconds)
Execution Context Reuse: Initialize SDK clients outside handler for reuse
/tmp Storage: Persists between invocations in same environment

Exam Focus Areas

Initialize SDK clients OUTSIDE the handler function for execution context reuse
Use Lambda Layers for shared dependencies (up to 5 layers, 250 MB total)
Lambda versions are IMMUTABLE - use aliases for traffic shifting
Enable X-Ray tracing with AWSXRayDaemonWriteAccess policy
Use Lambda Destinations instead of DLQ for async invocations (more flexibility)

Lambda Advanced Patterns

Versions, aliases, layers, and deployment strategies

Versions and Aliases

Versions

Immutable snapshots of function code + configuration. $LATEST is mutable.

Aliases

Pointers to specific versions. Can route traffic between two versions (weighted).

Traffic Shifting

Canary deployments using alias routing weights (e.g., 90% v1, 10% v2).

CodeDeploy Integration

Linear10PercentEvery1Minute, Canary10Percent5Minutes, AllAtOnce

Lambda Layers

ZIP archives containing libraries, custom runtimes, or dependencies
Up to 5 layers per function, 250 MB total unzipped
Extracted to /opt directory at runtime
Can be shared across functions and accounts

Lambda@Edge vs CloudFront Functions

Feature	Lambda@Edge	CloudFront Functions
Runtime	Node.js, Python	JavaScript only
Execution Time	5-30 seconds	< 1 millisecond
Memory	128 MB - 10 GB	2 MB
Network Access	Yes	No
Use Cases	Origin request/response manipulation	Viewer request/response (headers, URL rewrites)

Event Source Mapping Details

• Kinesis/DynamoDB Streams: Parallelization factor up to 10 per shard

• SQS: Batch size 1-10,000, long polling enabled automatically

• SQS FIFO: Scales by number of message groups

• Failure Handling: Bisect batch on error, max retry attempts, max record age

Exam Focus Areas

Use environment variable AWS_LAMBDA_FUNCTION_VERSION to detect current version
Lambda@Edge cannot use environment variables or layers
SQS queue triggers batch window and batch size for efficient processing
Use ReportBatchItemFailures for partial batch success with SQS

AWS Step Functions

Orchestrate serverless workflows with state machines

Step Functions Types

Type	Execution	Duration	Pricing	Use Cases
Standard	Exactly-once	Up to 1 year	Per state transition	Long-running workflows
Express	At-least-once	Up to 5 minutes	Per execution + duration	High-volume event processing

State Types

Task

Execute work (Lambda, AWS service, Activity)

Choice

Conditional branching based on input

Parallel

Execute branches concurrently

Wait

Delay for specified time

Map

Iterate over array items

Pass

Pass input to output (transform data)

Succeed/Fail

End execution with success/failure

Other Serverless Services

• EventBridge: Serverless event bus (rules, targets, schemas)

• AppSync: Managed GraphQL API service

• SAM: Serverless Application Model (CloudFormation extension)

Exam Focus Areas

Use Step Functions for workflows longer than Lambda timeout (15 min)
Express workflows for IoT data processing, high-volume streaming
Use Map state for parallel processing of array items
Callback pattern with Task tokens for human approval workflows

AWS Developer Associate Study Notes

AWS Lambda Core Concepts

Serverless compute service - the foundation of serverless development

Exam Domain

Development with AWS Services represents approximately 32% of the exam. Lambda is heavily tested.

Lambda Execution Model

Invocation Type	Behavior	Services	Error Handling
Synchronous	Caller waits for response	API Gateway, ALB, Cognito, Alexa	Caller handles errors
Asynchronous	Lambda queues event, returns 202	S3, SNS, EventBridge, SES	2 retries, then DLQ
Event Source Mapping	Lambda polls for records	Kinesis, DynamoDB Streams, SQS	Retry until success or record expires

Lambda Function Configuration

Setting	Description	Limits/Best Practices
Memory	128 MB to 10,240 MB	CPU scales proportionally with memory
Timeout	Maximum execution time	1 second to 15 minutes max
Ephemeral Storage	/tmp directory	512 MB to 10,240 MB
Environment Variables	Key-value configuration	4 KB total, use Secrets Manager for secrets
Reserved Concurrency	Limits concurrent executions	Protects downstream resources
Provisioned Concurrency	Pre-warmed execution environments	Eliminates cold starts, extra cost

Critical Lambda Limits

• Deployment Package: 50 MB zipped (direct upload), 250 MB unzipped

• Container Image: Up to 10 GB

• Concurrent Executions: 1,000 per region (soft limit)

• Invocation Payload: 6 MB (sync), 256 KB (async)

Lambda Execution Context

Cold Start: First invocation initializes execution environment (1-3 seconds)
Warm Start: Reuses existing environment (milliseconds)
Execution Context Reuse: Initialize SDK clients outside handler for reuse
/tmp Storage: Persists between invocations in same environment

Exam Focus Areas

Initialize SDK clients OUTSIDE the handler function for execution context reuse
Use Lambda Layers for shared dependencies (up to 5 layers, 250 MB total)
Lambda versions are IMMUTABLE - use aliases for traffic shifting
Enable X-Ray tracing with AWSXRayDaemonWriteAccess policy
Use Lambda Destinations instead of DLQ for async invocations (more flexibility)

Lambda Advanced Patterns

Versions, aliases, layers, and deployment strategies

Versions and Aliases

Versions

Immutable snapshots of function code + configuration. $LATEST is mutable.

Aliases

Pointers to specific versions. Can route traffic between two versions (weighted).

Traffic Shifting

Canary deployments using alias routing weights (e.g., 90% v1, 10% v2).

CodeDeploy Integration

Linear10PercentEvery1Minute, Canary10Percent5Minutes, AllAtOnce

Lambda Layers

ZIP archives containing libraries, custom runtimes, or dependencies
Up to 5 layers per function, 250 MB total unzipped
Extracted to /opt directory at runtime
Can be shared across functions and accounts

Lambda@Edge vs CloudFront Functions

Feature	Lambda@Edge	CloudFront Functions
Runtime	Node.js, Python	JavaScript only
Execution Time	5-30 seconds	< 1 millisecond
Memory	128 MB - 10 GB	2 MB
Network Access	Yes	No
Use Cases	Origin request/response manipulation	Viewer request/response (headers, URL rewrites)

Event Source Mapping Details

• Kinesis/DynamoDB Streams: Parallelization factor up to 10 per shard

• SQS: Batch size 1-10,000, long polling enabled automatically

• SQS FIFO: Scales by number of message groups

• Failure Handling: Bisect batch on error, max retry attempts, max record age

Exam Focus Areas

Use environment variable AWS_LAMBDA_FUNCTION_VERSION to detect current version
Lambda@Edge cannot use environment variables or layers
SQS queue triggers batch window and batch size for efficient processing
Use ReportBatchItemFailures for partial batch success with SQS

AWS Step Functions

Orchestrate serverless workflows with state machines

Step Functions Types

Type	Execution	Duration	Pricing	Use Cases
Standard	Exactly-once	Up to 1 year	Per state transition	Long-running workflows
Express	At-least-once	Up to 5 minutes	Per execution + duration	High-volume event processing

State Types

Task

Execute work (Lambda, AWS service, Activity)

Choice

Conditional branching based on input

Parallel

Execute branches concurrently

Wait

Delay for specified time

Map

Iterate over array items

Pass

Pass input to output (transform data)

Succeed/Fail

End execution with success/failure

Other Serverless Services

• EventBridge: Serverless event bus (rules, targets, schemas)

• AppSync: Managed GraphQL API service

• SAM: Serverless Application Model (CloudFormation extension)

Exam Focus Areas

Use Step Functions for workflows longer than Lambda timeout (15 min)
Express workflows for IoT data processing, high-volume streaming
Use Map state for parallel processing of array items
Callback pattern with Task tokens for human approval workflows