Sometimes it seems like you can hardly go a day without hearing about how “serverless” is going to change the world of backend architecture. But aside from toy proofs of concept, how are you realistically supposed to put it into practice? Most of us work with years-old codebases that are resistant to decoupling, much less easy to transition to serverless. Come hear how Yelp has been moving a 10 year old codebase from tangled spaghetti toward a serverless future using AWS Step Functions (SFN). You’ll gain familiarity with SFN as infrastructure, learn how it can be used to effectively disentangle complicated systems, and understand how to incrementally introduce serverless components into your monolithic application.

1. From monolithic to serverless
with Amazon Step Functions
@scott_triglia

2. Yelp’s Mission:
Connecting people with great
local businesses.

3. @scott_triglia
I work with 💵💶

4. Enforced audience
participation time!

5. The grass is always greener
CC BY 2.0 - royalty free

6. CC BY 2.0 - royalty free

7. CC BY 2.0 - royalty free

9. Our goals:
What is the SFN framework
Onboarding and immediate benefits
Building toward a serverless future

10. Subscription billing at Yelp
Monthly invoicing for advertising accounts
Business critical, happens at scale (>100k accts)

11. Subscription billing at Yelp
bill all
accounts
collect all
accounts
create
invoices

12. Migration Challenges
No good API existed for the
business process
Very far from being
lambda-compatible
Not nicely factored into
small pieces
Amazon API
Gateway
Amazon
Lambda

13. What is Step Functions?

14. Pretty diagrams as a service!

15. Monitoring the status of a report

16. Long-running batch jobs

17. …or even more complicated flows!

18. Get started…
Write some JSON
Get a state machine!

19. …and just implement functions!

20. …and just implement functions!
Local
Process

21. …and just implement functions!
Amazon
Lambda

22. …handle errors gracefully!
Trap errors and
take different paths

23. …and lots more!
https://aws.amazon.com/documentation/step-functions/

24. CC BY 2.0 - royalty free
back to that promised future..

25. Subscription billing at Yelp
Monthly invoicing for advertising accounts
Business critical, happens at scale (>100k accts)

26. Subscription billing at Yelp
bill all
accounts
collect all
accounts
create
invoices

27. Subscription billing at Yelp
bill all
accounts
collect all
accounts
create
invoices

28. Migration Challenges
Not great observability
Older code, evolved over
~10 years
bill all
accounts

29. Old logic
bill all
accounts
def runner(all_accounts):
for chunk in all_accounts:
dispatch_work(chunk)
def worker(chunk):
for account in chunk:
bill_account(account)

30. Monolith to service-like workflows
bill all accounts
bill all
accounts

31. Act like a service
{
“account_id”: 142,
“date”: “2017-09-27”,
}

32. API driven where lambdas aren’t yet practical
"Bill Account": {
"Type": "Task",
"Resource": “arn:aws:states:us-
west-2:1234:activity:bill-account",
},

33. Benefits

34. Benefits - execution parallelism
Easily modify parallelism
factor
Native parallelism offers
significant speedup
bill all accounts

35. Benefits - flexible timeouts
“Bill Account": {
…
"TimeoutSeconds": 1200,
"HeartbeatSeconds": 60,
…
}

36. Benefits - enhanced observability
Explicitly represent and
handle failure modes
Easily observed
Execution-level failures
become a huge red flag

37. Benefits - safe refactoring

38. Building toward a
serverless future

39. SFN benefits
Flexible execution model works:
from monolith
…to microservices
…to lambdas

40. SFN benefits
Enforced decoupling
Native Parallelism
Free observability

41. SFN benefits
A strong foundation for
future experimentation

42. Bill one account

43. Bill one account

44. Bill one account

45. Bill one account

46. Bill one account

49. CC BY 2.0 - royalty free

50. @YelpEngineering
fb.com/YelpEngineers
engineeringblog.yelp.com
github.com/yelp
@scott_triglia