1. Refactoring to Serverless Translating
common application architecture patterns to
serverless on AWS
Adithya Reddy & Prashanth HN

2. Adithya Reddy
Who Are We?
@TheTallpants
github.com/tallpants
SDE, Branch Insurance
Prashanth HN
@prashanth
github.com/hnprashanth
CTO, WheelsBox

3. Source: AWS

4. • External / Centralized Configuration
• Circuit Breakers & Retries
• Real time / web-sockets
• Asynchronous background tasks
Just Another Serverless talk?
Hell No!

5. Circuit Breakers &
Retries

6. What’s a Circuit Breaker?
Circuit breaker is a design pattern used in modern
software development. It is used to detect failures
and encapsulates the logic of preventing a failure
from constantly recurring, during maintenance,
temporary external system failure or unexpected
system difficulties

7. Circuit Breakers
• Allow systems to "open" the circuit when constant failures
happen repeatedly giving immediate failure responses
instead of loading the system. It can later try "half open"
and see if the system is functioning fine now and "close" in
case things are back to normal, making it self-healing.
• Allow us to contain failures and stop them from creating a
cascading effect of other parts.

8. Circuit Breaker Using Lambda
Source: https://www.jeremydaly.com/serverless-microservice-patterns-for-aws/

9. Circuit Breaker Using Step Functions
Source: https://tech.trivago.com/2019/04/09/circuit-breaker-with-aws-step-functions/

10. External / Centralized
Configuration

12. Configuration is immutable for each
published version
1.
2.

13. Config Servers

14. Source: gocd.org

15. • Refresh config values while your app is still running.
• Your app can choose when to refetch configuration
• Per request
• Time-based refetch
• Etc.

16. SSM Parameter Store

18. • Secure hierarchical storage for configuration and secrets
• Store as plain text / KMS encrypted strings
• Reference by unique name
• Version history, access control at key / hierarchy level
• Configurable on-change triggers via CloudWatch Events
• CloudWatch + CloudTrail
• Reference-able asTerraform data source (and CloudFormation – but only
specific versions of keys)
• Generous free limits (1000TPS free, $0.05 per 10,000TPS)

19. Hierarchical configuration

20. Access Control
Standard
ABAC /Tag based

23. github.com/tallpants/ssm-parameter-store
Safer, nicer abstraction over SSM parameter store with built-in caching, idempotent
preloading, TypeScript compile time checks, and handy autocompletion

25. Asynchronous
BackgroundTasks

26. Limitations of Lambda
• Resource limitations of Lambda: storage etc
• Lambdas will timeout after 15 minutes
• Limitations in tech stack & stack customisation

27. Amazon ECS

28. AWS Fargate

29. Example Architecture – Resize image to multiple
sizes

30. Advantages
• SQS can be integrated with almost any kind of service
allowing wide set of triggers
• Auto-scale without hassle
• No infrastructure to manage
• Per second billing (min 1 minute) for the resources used,
vCPU & memory
• Easy to handle failures and retries

31. RealTime / Web-
Sockets

33. Source: AWS

34. API Gateway
Websocket
Endpoint URL
wss://… connectionId connectionId

35. API Gateway
Websocket
Endpoint URL
4. Body sent
to client
3. HTTP POST to
/connectionId
2. Get active
connectionIds
1. Score
update
event
wss://…

38. Questions?

39. Adithya Reddy
Who Are We?
@TheTallpants
github.com/tallpants
SDE, Branch Insurance
Prashanth HN
@prashanth
github.com/hnprashanth
CTO, WheelsBox