This document provides guidance on migrating existing applications to a serverless architecture using AWS services, emphasizing the benefits of reduced infrastructure management and automatic scaling. It outlines a step-by-step approach for transitioning monolithic applications by identifying seams in the code, organizing data, and utilizing AWS Lambda alongside other services. The document encourages gradual migration and emphasizes best practices for building and managing serverless applications effectively.

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How to migrate an existing
application to serverless
Marcia Villalba
Developer Advocate AWS
@mavi888uy

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About me
AWS Developer Advocate
Working with serverless since 2015
Host of FooBar YouTube Channel
https://youtube.com/foobar_codes
@mavi888uy

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2 stories
rovio
Not that
successful story
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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Function as a Service (FaaS)
“AWS Lambda lets you run code without
provisioning or managing servers. ...
…Just upload your code and Lambda takes care
of everything required to run and scale your code
with high availability.
You can set up your code to automatically
trigger from other AWS services or call it directly
from any web or mobile app”
AWS – Lambda definition
AWS
Lambda

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How AWS Lambda works?
Event source Function Services
Node.js
Python
Java
C#
Go
Custom runtimes
Changes in
data state
Requests to
endpoints
Changes in
resource state
Amazon S3
DynamoDB
Amazon
SQS
APIs
Business
logic

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Managed services
Amazon S3
Amazon SQS
DynamoDB

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Story 1

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Managing unknowns

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Lack of technology knowledge

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Will this solve my problem?

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Foundational work

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Conway Law
”Any organization that designs a system will inevitably
produce a design whose structure is a copy of the
organization communication structure…”
Melvin Conway
Reverse Conway’s maneuver
Structure your organization to match the software you
would like to build
Small, agile teams – Two pizza teams

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Pick your tools
- Programming languages
- Deployment frameworks
- Developer tools

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Use Infrastructure as code
1. Minimize risk and bugs
2. Make infrastructure changes
repeatable and predictable
3. infrastructure changes using the
same tools as code changes

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CI/CD

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Check my other talk in the
conference later today J

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Monitoring and observability
Make sure that all your services send
metrics and logs
Pick a centralized tool for handling this

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Observability in AWS
CloudWatch
Insights
CloudWatch
Alarms
CloudWatch
Dashboard
CloudWatch
ServiceLens

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AWS Lambda Power Tools
Tracing - Decorators and utilities to trace Lambda function handlers, and both
synchronous and asynchronous functions
Logging - Structured logging made easier, and decorator to enrich structured
logging with key Lambda context details
Metrics - Custom Metrics created asynchronously via CloudWatch Embedded
Metric Format (EMF)
https://github.com/awslabs/aws-lambda-powertools-python
https://github.com/awslabs/aws-lambda-powertools-java
https://github.com/getndazn/dazn-lambda-powertools

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The big rewrite
Please don’t do it

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Story 2

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29. 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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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

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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

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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

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

36. 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.

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

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comicrelief.com/donate

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The strangler pattern

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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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Step 1 – Find the seams in the code
”… a seam is a portion of the code that can be treated
in isolation and worked on without impacting the rest
of the codebase…”
Michael Feathers

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Step 1 – Find the bounded context in the code
Examples of seams in Java
Package content
- Organize your code inside different packages if its not done already
Example of seams in Javascript
Modules
- Be careful when moving things around if you don’t have unit tests.

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Big mess of Customer, orders and inventory business logic
OrderId Order info
CustomerId Customer
info…
CustomerId OrderId OrderId ItemId
ItemId Item info
DB manager
Authentication / User management

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ItemsCustomersOrders
OrderId Order info
CustomerId Customer
info…
CustomerId OrderId OrderId ItemId
ItemId Item info
DB manager
Authentication / User management

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Package1
Repository1
Package2
Repository2
PackageN
Repository
N
Monolithic application
DB
Step 2 – Organizing the data

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ItemsCustomers Orders
OrderId Order info
CustomerId Customer
info…
CustomerId OrderId
OrderId ItemId
ItemId Item info
DB order manager
DB customer
manager
DB items manager
Authentication / User management

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Step 3 – Move the code gracefully
1. Choose what to
migrate first
2. Rebuild it as a
serverless component
Tidy
Monolith
Users
DB
Tidy
Monolith
Service1
LB
Users
DBDB

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Where to start?
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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Recommended strategy
Start with the least critical
part of your system (2 or 3
services)
Then move the most critical
part

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Express tips to design serverless
applications

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

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Microservices architectures
Mobile client
Client
IoT
API
Gateway
Shipping DB
Inventory DB
Store Front
Web App
Shipment
Query
Inventory
Query
Logical microservice
AWS Lambda
AWS Lambda
AWS Lambda
SQS
Amazon DynamoDB

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Integration options from AWS
Amazon
API Gateway
Amazon
SQS
Amazon
SNS
AWS
Step Functions
APIs Choreography Orchestration
Amazon
EventBridge

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APIs are the front door of microservices

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Microservices architectures
Shipment
serviceCustomer
service
API
Gateway

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Track status of data
and execution
Remove
redundant code
Build workflows to orchestrate everything

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Single responsibility principle
“A class should have only one reason to change”
Robert C. Martin – Uncle Bob
In the serverless worlds this means:
- Simpler functions – easier to know what they are doing
- Less code to test
- Single purpose functions are more secure
- Single purpose functions perform better

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Single responsibility principle
“A class should have only one reason to change”
Robert C. Martin – Uncle Bob
In the serverless worlds this means:
- Simpler functions – easier to know what they are doing
- Less code to test
- Single purpose functions are more secure
- Single purpose functions perform better
However, you need to find the right balance on
the size of the function – not to big or too small

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DB
Coordinating functions can be hard
Queue

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Turning functions into microservices
“I want to select functions based on data”
“I want to retry functions”
“I want try/catch/finally”
“I have code that runs for hours”
“I want to sequence functions”
“I want to run functions in parallel”

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AWS Step Functions
Resilient workflow automation
Built-in error handling
Powerful AWS service integration
First-class support for integrating with
your own services
Auditable execution history and visual monitoring
Fully-managed state machines on AWS

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AWS Cloud
House owners
AWS Step Functions workflow
Validate owner
Validate property
Validation Successful
Validation Not Successful
Validated?
Amazon API Gateway
Add a
property
Amazon EventBridge
Properties
service
Messaging
service
Validator service

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Choreography
Event-driven architectures

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Decouple state from code using messaging
Queues
Simple
Fully-managed
Any volume
Pub/sub
Simple
Fully-managed
Flexible
Amazon Simple
Queue Service
Amazon Simple
Notification
Service
Messaging
Synchronization
Rapid
Fully-managed
Real-time
Amazon
EventBridge
- Independent releases
- Scalability
- Modular code
- Easy to maintain and to work on
- Adds resiliency to the application

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So why we need decoupling?

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Event bus to help us to decouple our microservices

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Mobile client
Client
IoT
API
Gateway
Shipping DB
Inventory DB
Store Front
Web App
Shipment
Query
Inventory
Query
Logical microservice
AWS Lambda
AWS Lambda
AWS Lambda
SQS
Amazon DynamoDB

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

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Serverless analytics pipeline
Amazon Cognito
Amazon S3 Users
Amazon
Kinesis Data
Firehose
Amazon
Athena
AWS Glue Amazon
QuickSight
S3
Bucket
AWS Cloud
Client

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Step 4 - Breaking the database
Logical microservices should own their data
Migrate the data to the new database
Rethink how your data is stored – noSQL, files, SQL, ect.

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Step 5 – Breaking the APIs
We need to keep the APIS compatible after migration for our clients
We want to switch the traffic to the new service gradually

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Move traffic gradually to the new service
Tidy Monolith with
old service 1
Service1
Application Load
Balancer
Users
30% traffic
70% traffic
ALB Weighted Target Groups

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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
Marcia Villalba
@mavi888uy
FooBar YouTube Channel
https://youtube.com/foobar_codes