Service Communication

Question 1

Step Functions

Answer 1

• Represent flow as Json State Machine
• Max execution time of 1 year
• Human approval flows
• Add latency because of passing calls
• No integration with Mechanical Turk

Question 2

Step Functions

Answer 2

• Lambda Tasks
• Activity Tasks
• • HTTP Activity worker, backed by EC2, Mobile Device, on-prem Data Center
• • Poll Step Functions service , is there an activity for me to do?
• Service Task
• • AWS Service integration
• Wait Task, for the duration or until timestamp

Question 3

Step Functions - User Case Triggers

Answer 3

• Rest Api call from API Gateway
• CW Events
• AWS SDK/CLI

Question 4

Simple Workflow Service (Legacy)

Answer 4

• Mechanical Turk integration
• Not serverless, EC2
• 1 year max runtime
• Activity, decision and human intervention steps
• Good for:
• • External signals intervening in the workflow
• • Child processes that return values to parent processes

Question 5

SQS

Answer 5

• Serverless, IAM integration
• Extreme scale, no provisioning required
• Max message size 256KB, use S3 pointer for larger

Question 6

SQS Use Cases

Answer 6

• Can be read from EC2, Lambda

- Can be used as write buffer for DDB (throttling)

Question 7

SQS FIFO

Answer 7

• Preserve sent order
• 300 messages/s without batching
• 3000 messages with batching

Question 8

Event Source Mapping SQS && SQS FIFO

Answer 8

• Long Poll SQS
• Specify Batch size
• Set queue visibility to be 6x that of lambda function

Question 9

Dynamo DB Idempotence

Answer 9

Insert NOT idempotent

Upsert IS idempotent

Question 10

SQS DLQ

Answer 10

• Setup from SQS directly
• DLQ for lambda is only for async invocations
• OR use a Lambda Destination to have DLQ from Lambda

Question 11

Amazon MQ vs SQS

Answer 11

• For traditional/open protocols
• AWS protocols for SQS/SNS are proprietary and will require application refactor, phased migration
• Doesn’t scale as much
• Runs on dedicated machine, can run in HA for failover

Question 12

SNS

Answer 12

• Pub/Sub, one SNS as many consumers as desired
• Can filter messages (new features)
• Up to 10,000,000 subscriptions per topic
• 100,000 topics limit
• Delivery retries for HTTP/HTTPS

Question 13

SNS - SQS Fanout

Answer 13

• Ensure delivery between SNS and SQS, no data loss
• Fully decoupled
• Can add consumers at any time (later)
• SQS allows for delayed processing, retries
• Processing can be at different speed

Question 14

Kinesis

Answer 14

Gives scale and also allows allows ordering by partition key