The document discusses strategies for migrating existing applications to serverless architectures. It outlines a 5-step process: 1) find seams in monolithic code; 2) organize code into logical services; 3) gracefully move code to serverless functions; 4) break apart monolithic databases; 5) break apart monolithic APIs. Tips are provided for designing serverless applications using microservices, event-driven architectures, and managed services. A case study describes how Comic Relief migrated their donation platform using these strategies to reduce costs and improve scalability.

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How to migrate an existing
application to serverless
Marcia Villalba
@mavi888uy

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About me
AWS Developer Advocate
Coding for more than 15 years
Host of FooBar YouTube Channel
https://youtube.com/foobar_codes

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2 stories
rovio
Successful story
Not that
successful story

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Serverless
”Serverless is a
methodology for
planning, building and
deploying software in a
way that maximizes value
by minimizing
undifferentiated heavy
lifting…”
Jeremy Daly

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What it means that something is serverless?
No managing infrastructure High availability built in
Pay for what you useScales automagically

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7. @theburningmonk

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Story 1

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The big
rewrite
Please don’t do it
Strategy 1

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Story 2

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13. SCALING CHALLENGES
350
DONATIONS PER SECOND

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2016
Drupal 7 monolith
- Static content
- Pay-in fundraising
- Gift aid declaration
- Fundraiser gallery
- Contact us
Giving
Pages
Donate

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Where to start migrating?
Strategy 1
Start with the least critical
part of your system
Strategy 2
Start with the part of the
system with the highest
return of invested time
🤔

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2017
Drupal 7 monolith
- Static content
- Contact us
Drupal 8
- Static content
Pay-in
fund-
raising
SMS
Gift aid
Fundraise
gallery
Giving
Pages
Donate

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2018
Drupal 8
- Static content
Pay-in fund-
raising
SMS
Gift aid
Giving
Pages
Donate
Contact
us
Red Nose
Comp
School
step calc

18. © 2020, Amazon Web Services, Inc. or its Affiliates.
2018
Drupal 8
- Static content
Pay-in fund-
raising
SMS
Gift aid
Contact
usGiving
Pages
Donate
Red Nose
Comp
School
step calc
Mailer Service
Postcode lookup

19. © 2020, Amazon Web Services, Inc. or its Affiliates.
2019
Drupal 8
- Static content
Pay-in fund-
raising
Contact
us
Payment Service layer
Image uploader service
Marketing preferences service
Mailer Service
Postcode lookup service
SMS Gift
Aid
Donate

20. Donate
bit.ly/cr-donate-blueprint

21. OLD VS NEW
March 2019 cost*
$5,393
March 2015 cost*
$83,908
*All hosting costs are paid for through corporate partnerships.
100% of public donations go to the projects we fund.

22. WE COULD DO
IT ALL AGAIN TOMORROW
Serverless services cost
$92

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comicrelief.com/donate

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Strategy 2 - Strangler pattern
Monolith
Users
DB
Monolith
Service1
LB
Users
DBDB
Monolith
LB
Service1 Service n
Users
DB DB DB

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Steps for doing the strangler pattern
Migrating to serverless in 5 steps

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Foundational work

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Things to do before getting started
- Reverse Conway manuover
- Pick your tools
- Use infrastructure as code
- CI/CD pipeline
- Monitoring and observability

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Steps
1. Find the seams of the code – if you have a monolith

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Steps
1. Find the seams of the code – if you have a monolith
2. Organize the code inside the monolith

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Steps
1. Find the seams of the code – if you have a monolith
2. Organize the code inside the monolith
3. Move the code gracefully

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Express tips to design serverless
applications

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EXPRESS TIPS TO DESIGN SERVERLESS APPS
1. Logical microservices

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Tidy Monolith
LB
Users
Logical microservice
AWS Lambda AWS Lambda
AWS Lambda AWS Lambda
AWS Lambda
DB
DB

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EXPRESS TIPS TO DESIGN SERVERLESS APPS
1. Logical microservices
2. Event – driven architectures

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Decoupling the services and functions
- Independent releases
- Scalability
- Modular code
- Easy to maintain and to work on
- Adds resiliency to the application Amazon Simple
Notification
Service
Amazon Simple
Queue Service
Amazon
EventBridge

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Why do you need a router?

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EXPRESS TIPS TO DESIGN SERVERLESS APPS
1. Logical microservices
2. Event – driven architectures
3. Replace what you can with managed services

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Replace existing functionality with managed services
Amazon Cognito
Order service
Customer
service
Items service
Users

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Steps
1. Find the seams of the code – if you have a monolith
2. Organize the code inside the monolith
3. Move the code gracefully
4. Break the database

40. © 2020, Amazon Web Services, Inc. or its Affiliates.
Steps
1. Find the seams of the code – if you have a monolith
2. Organize the code inside the monolith
3. Move the code gracefully
4. Break the database
5. Break the APIs

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Closing remarks

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Steps start migrating
1 – Do the foundational work
2 – Move your monolith to the cloud if needed
3 – Find the seams for your code
4 – Organize the data layer
5 – Move the code to serverless
6 – Break the database
7 – Break the APIs
8 – Repeat from step 5 until 7 until you are done

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Thanks a lot
Marcia Villalba
Developer Advocate AWS
Twitter: @mavi888uy
YouTube: https://youtube.com/foobar_codes