How can you take an existing monolith to the cloud with very minimal effort? In this talk we will explore an architecture that can help you to achieve that while focusing on scalability and resilience.

1. Let's take the monolith to the cloud 🚀
Luciano Mammino ( )
@loige
loige.link/mono-lit
2022-03-01
1

2. @loige
Get the slides! 👇
loige.link/mono-lit
2

3. I'm Luciano 👋
Senior Architect @ fourTheorem (Dublin )
nodejsdp.link
📔Co-Author of Node.js Design Patterns 👉
Let's connect!
(blog)
(twitter)
(twitch)
(github)
loige.co
@loige
loige
lmammino
3

4. We are business focused
technologists that deliver.
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Accelerated Serverless AI as a Service Platform Modernisation
We are hiring
do you want to ?
work with us
loige 4

5. I co-host a podcast about AWS with !
@eoins
@loige
awsbites.com Pleaze, subscribe 😇
5

6. @loige
Story time
6

7. @loige
Story time
7

8. @loige
Story time
8

9. @loige
Story time
9

10. Business Summary
@loige
SaaS CMS for legal practices
1 founder + 1 developer
💸Bootstrapped business
🙌Good MVP, getting attention in the market
💪Started a TRIAL with a big customer
10

11. Current problems
@loige
📈The company is growing
⚖but the technology does not scale!
📦1 monolithic server
🔥Frequent failures = 🤬unhappy customers
😥The business is at risk!
11

12. Desired State
@loige
⚖More reliable & scalable infrastructure
👌Minimal amount of change required*
* the team is not skilled with the cloud & containers, we need to keep cognitive load low
12

13. @loige
🤔
"I heard that the cloud is great but we don't
have the time and the skills to re-architect
everything as micro-services!"
13

14. 🧐
What can we
recommend?
@loige
14

15. ⛏
Let's start to
dig deeper!
@loige
15

16. Example use cases
@loige
A user logs in the application and they should be able to see
all their previously uploaded legal documents
A user can upload new documents and organize them by
providing specific tags (client id, case number, etc.)
A user might search for documents containing specific
keywords or tags
16

17. Current Architecture*
@loige
Virtual Private Server
* a beautiful monolith ❤ 17

18. Can we take the monolith to
the cloud and make it resilient
& scalable?
@loige
18

19. Load Balancer
App Server(s)
File Storage Session Storage
Database
Target architecture
@loige
19

20. 🧐
Let's get more specific...*
@loige
* Mostly AWS from here
20

21. S3 ElastiCache
RDS
Application Load Balancer
EC2 Instance(s)
Target architecture on AWS
@loige
21

22. ✋
Let's pause
for a second...
@loige
22

23. 🤔
What is the cloud, really?
@loige
23

24. @loige
24

25. ... a little more involved
than that! 😅
@loige
25

26. ☁The "cloud" is built...
@loige
To scale
To be resilient
26

27. OK, but how?! 😒
@loige
27

28. Region
@loige
A physical location around the world (e.g. North
Virginia, Ireland or Sydney) where AWS hosts a group
of data centers.
Regions help to provision infrastructure that is closer
to the customers, so that our applications can have
low latency and feel responsive.
28

29. Availability Zone (AZ)
@loige
Discrete data center with redundant power,
networking, and connectivity in an AWS Region.
Data centers in different availability zones are
disjointed from one another, so if there’s a serious
outage, that’s rarely affecting more than one
availability zone at the same time.
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30. Availability Zone (AZ)
@loige
It’s good practice to spread redundant infrastructure
across different availability zones in a given region to
guarantee high availability.
30

31. VPC
@loige
A virtual (private) network provisioned in a given
region for a given AWS account.
It is logically isolated from other virtual networks in
AWS.
Every VPC has a range of private IP addresses
organised in one or more subnets.
31

32. Subnet
@loige
A range of IPs in a given VPC and in a given availability
zone that can be used to spin up and connect
resources within the network.
Subnets can be public or private.
A public subnet can be used to run instances that can
have a public IP assigned to them and can be
reachable from outside the VPC itself.
32

33. Subnet
@loige
It’s good practice to keep front-facing servers (or load
balancers) in public subnets and keep everything else
(backend services, databases, etc.) in private subnets.
Traffic between subnets can be enabled through
routing tables to allow for instance a load balancer in a
public subnet to forward traffic to backend instances
in a private subnet.
33

34. Quick Recap
@loige
Region: physical location with data centers
Availability Zone: data center in a region
VPC: a virtual private network in a region
Subnet: range of IPs in a VPC in a given AZ
34

35. @loige
Region
AZ1 AZ2 AZ3
VPC
Subnet
Resource
(e.g. EC2 instance)
35

36. ✏TODO List
@loige
☐ Create an AWS account
☐ Select a region
☐ Create and configure a VPC
36

37. Our VPC
@loige
37

38. ☑ Create an AWS account
☑ Select a region
☑ Create and configure a VPC
✏TODO List
@loige
38

39. ✏TODO List
@loige
☐ Load Balancer
☐ EC2
☐ S3
☐ RDS
☐ ElastiCache
☐ Route 53
39

40. Application Load Balancer (ALB)
@loige
The entry point to all the application traffic.
Layer 7 Load Balancer (HTTP, HTTPS, WebSocket,
gRPC).
Highly available: replicated in all our public
subnets.
40

41. Application Load Balancer (ALB)
@loige
Scalable: can handle millions of request per
second.
Managed service: we don't need to configure the
OS or install software patches.
Can be integrated with ACM (AWS Certificate
Manager) to support HTTPS.
41

42. Application Load Balancer (ALB)
@loige
Target group 42

43. Application Load Balancer (ALB)
@loige
Target group
🔥
/health
✅
❌
/health
/health
✅
Unhealty targets
won't get any traffic
43

44. Application Load Balancer (ALB)
@loige
Targets can be added dynamically.
We can scale targets automatically using
autoscaling groups.
E.g. Add or remove instances based on num
requests in-flight or on avg CPU of the current
instances.
44

45. How does it scale?
@loige
Being a managed service, scalability is mostly
handled out of the box by AWS.
45

46. Resiliency
@loige
A load balancer can distribute traffic to multiple
AZs, so if one of them becomes unavailable it will
keep distributing traffic to the remaining ones.
46

47. ✏TODO List
@loige
☑ Load Balancer
☐ EC2
☐ S3
☐ RDS
☐ ElastiCache
☐ Route 53
47

48. EC2 - Virtual Machine
@loige
Virtual machine running all the necessary
software for the service (Nginx, Node.js, app code,
etc.)
They need to use Security Groups (allow traffic)
and IAM Roles (allow them to access other AWS
resources like S3).
48

49. EC2 - Virtual Machine
@loige
We will need to provision multiple machines
dynamically.
Challenges:
Consistency
🐮Cattle vs 🙀Pet mindset
Stateless applications
49

50. Consistency
@loige
All our virtual machines have to be the same: we
need to build an AMI (Amazon Machine Image).
An AMI contains OS, libraries, software and source
code.
You can use an AMI to start a new instance.
50

51. Consistency
@loige
While we can build an AMI manually, it's better to
use tools to automate the work:
Hashicorp Packer
EC2 Image Builder
51

52. 🐮Cattle vs 🙀Pet mindset
@loige
Once an instance has been launched we shouldn't
change it anymore (e.g update the OS, install new
softare, update the code, etc.)
If we need to change something, we build a new
image and deploy new instances.
Instances are disposable!
52

53. Stateless
@loige
We are load balancing traffic so a user might be
served by different instances during their session.
A single instance should not store any state (e.g.
user sessions, uploaded files, etc.)
State should be stored outside instances
(ElastiCache, S3, RDS, etc).
53

54. Stateless
@loige
Making an application stateless might require a
good amount of code change.
A shortcut to this might be to enable
in the ALB, but it's not recommended for
scalability and resiliency.
sticky
sessions
54

55. How does it scale?
@loige
Every instance will be able to handle a certain
number of requests per second.
We can scale by adding more instances when the
traffic grows.
55

56. Resiliency
@loige
We should have at least 1 instance per
availability zone.
If there is an AWS outage, the instances on the
healthy availability zone will keep handling
requests.
We can use an autoscaling group to make sure
that unhealthy instances are replaced.
56

57. ✏TODO List
@loige
☑ Load Balancer
☑ EC2
☐ S3
☐ RDS
☐ ElastiCache
☐ Route 53
57

58. Simple Storage Service (S3)
@loige
One of the very first AWS services and (probably)
the most famous one.
Object storage service: Allows you to store any
amount of data durably.
You need to use the SDK to read and write data.
58

59. Simple Storage Service (S3)
@loige
Data can be organised in logical containers called
Buckets.
Key/value model: Inside a bucket you can store
data by providing a key and the content.
59

60. Simple Storage Service (S3)
@loige
const AWS = require('aws-sdk')
const s3 = new AWS.S3()
const params = {
Bucket: 'my-bucket',
Key: 'my-first-s3-file.txt',
Body: Buffer.from('Hello, AWS')
}
s3.upload(params, (err) => {
if (err) {
console.error(err)
} else {
console.log('Upload successful')
}
})
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const AWS = require('aws-sdk')
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const s3 = new AWS.S3()
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const params = {
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Bucket: 'my-bucket',
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Key: 'my-first-s3-file.txt',
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Body: Buffer.from('Hello, AWS')
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}
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s3.upload(params, (err) => {
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if (err) {
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console.error(err)
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} else {
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console.log('Upload successful')
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}
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})
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const s3 = new AWS.S3()
const AWS = require('aws-sdk')
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const params = {
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Bucket: 'my-bucket',
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Key: 'my-first-s3-file.txt',
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Body: Buffer.from('Hello, AWS')
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}
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s3.upload(params, (err) => {
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if (err) {
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console.error(err)
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} else {
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console.log('Upload successful')
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}
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})
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const params = {
Bucket: 'my-bucket',
Key: 'my-first-s3-file.txt',
Body: Buffer.from('Hello, AWS')
}
const AWS = require('aws-sdk')
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const s3 = new AWS.S3()
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s3.upload(params, (err) => {
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if (err) {
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console.error(err)
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} else {
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console.log('Upload successful')
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}
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})
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s3.upload(params, (err) => {
if (err) {
console.error(err)
} else {
console.log('Upload successful')
}
})
const AWS = require('aws-sdk')
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const s3 = new AWS.S3()
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const params = {
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Bucket: 'my-bucket',
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Key: 'my-first-s3-file.txt',
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Body: Buffer.from('Hello, AWS')
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}
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const AWS = require('aws-sdk')
const s3 = new AWS.S3()
const params = {
Bucket: 'my-bucket',
Key: 'my-first-s3-file.txt',
Body: Buffer.from('Hello, AWS')
}
s3.upload(params, (err) => {
if (err) {
console.error(err)
} else {
console.log('Upload successful')
}
})
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60

61. Simple Storage Service (S3)
@loige
Too much code to change?
A first migration could be done by using a
something like to create a "virtual
filesystem" that allows you to read/write to S3
seamlessly.
s3fs-fuse
61

62. How does it scale?
@loige
S3 is a managed service which automatically
scales to thousands of read/write operations per
second.
62

63. Resiliency
@loige
S3 is provisioned in multiple AZs by default and it
makes multiple copies of your data.
All of this happens transparently, no special
configuration required.
63

64. ✏TODO List
@loige
☑ Load Balancer
☑ EC2
☑ S3
☐ RDS
☐ ElastiCache
☐ Route 53
64

65. Relational Database Service (RDS)
@loige
Managed relational database service for MySql,
PostgreSQL, MariaDB, Oracle & SQL Server.
Being a managed service, AWS takes care of most
common concerns like backups and updates
(configurable).
65

66. How does it scale?
@loige
RDS PostgreSQL supports Read Replicas: you can
provision additional instances to which you can
distribute heavy read-only queries.
66

67. Resiliency
@loige
RDS PostgreSQL can be configured to work in
Multi-AZ mode: this means that there will be one
or two standby copies of the database in different
AZs.
If the primary DB instance or the primary AZ have
an outage, one of the standby copies are
promoted to become "the primary" instance.
67

68. Resiliency
@loige
Failover is fast but not instantaneous (60-120
seconds), so we need to make sure to plan for
possible connectivity failures in your app and
show clear error messages to the users.
68

69. ✏TODO List
@loige
☑ Load Balancer
☑ EC2
☑ S3
☑ RDS
☐ ElastiCache
☐ Route 53
69

70. ElastiCache
@loige
Managed in-memory caching service supporting
Redis and Memcached.
Meant to be used for use cases that don't require
durability like data cache, session stores, gaming
leaderboards, streaming, and analytics.
AWS takes care of maintenance.
70

71. How does it scale?
@loige
A single instance of Redis (with enough memory)
can scale to significant amounts of traffic.
If you need more, you can run ElastiCache Redis in
Cluster Mode and shard your data across
multiple Redis instances.
71

72. Resiliency
@loige
ElastiCache Redis can operate in Multi-AZ mode.
Similarly to RDS, in case of failures, there might be
some downtime while the new master is
promoted.
We need to make sure the app accounts for Redis
connection failures.
72

73. ✏TODO List
@loige
☑ Load Balancer
☑ EC2
☑ S3
☑ RDS
☑ ElastiCache
☐ Route 53
73

74. Route53
@loige
Highly available and scalable cloud DNS service.
Can be used to direct traffic on a given domain to
our Application Load Balancer.
74

75. ✏TODO List
@loige
☑ Load Balancer
☑ EC2
☑ S3
☑ RDS
☑ ElastiCache
☑ Route 53
75

76. Infrastructure as Code (IaaC)
@loige
We could provision everything "manually" from
the web console, but...
It will be hard to create consistent
environments for development and QA
It will be hard to change things incrementally
How would we test and review changes before
applying them in production?
76

77. Infrastructure as Code (IaaC)
@loige
It's better to define all the infrastructure using code.
There are several tools that can help us with that:
CloudFormation
Hashicorp Terraform
Cloud Development Kit (CDK)
Pulumi
77

78. {
"AWSTemplateFormatVersion" : "2010-09-09",
"Description" : "AWS CloudFormation Sample Template EC2InstanceWithSecurityGroupSample: Create an Amazon EC2 instance running the A
"Parameters" : {
"KeyName": {
"Description" : "Name of an existing EC2 KeyPair to enable SSH access to the instance",
"Type": "AWS::EC2::KeyPair::KeyName",
"ConstraintDescription" : "must be the name of an existing EC2 KeyPair."
},
"InstanceType" : {
"Description" : "WebServer EC2 instance type",
"Type" : "String",
"Default" : "t2.small",
"AllowedValues" : [ "t1.micro", "t2.nano", "t2.micro", "t2.small", "t2.medium", "t2.large", "m1.small", "m1.medium", "m1.large"
,
"ConstraintDescription" : "must be a valid EC2 instance type."
},
"SSHLocation" : {
"Description" : "The IP address range that can be used to SSH to the EC2 instances",
"Type": "String",
"MinLength": "9",
"MaxLength": "18",
"Default": "0.0.0.0/0",
"AllowedPattern": "(d{1,3}).(d{1,3}).(d{1,3}).(d{1,3})/(d{1,2})",
"ConstraintDescription": "must be a valid IP CIDR range of the form x.x.x.x/x."
}
},
"Mappings" : {
"AWSInstanceType2Arch" : {
"t1.micro" : { "Arch" : "HVM64" },
"t2.nano" : { "Arch" : "HVM64" },
"t2.micro" : { "Arch" : "HVM64" },
@loige
Example of CloudFormation template
78

79. import * as cdk from '@aws-cdk/core'
import * as ec2 from '@aws-cdk/aws-ec2'
export class CdkUbuntuEc2Stack extends cdk.Stack {
constructor (scope: cdk.Construct, id: string, props?: cdk.StackProps) {
super(scope, id, {
env: {
account: process.env.CDK_DEPLOY_ACCOUNT || process.env.CDK_DEFAULT_ACCOUNT,
region: process.env.CDK_DEPLOY_REGION || process.env.CDK_DEFAULT_REGION
},
...props
})
const defaultVpc = ec2.Vpc.fromLookup(this, 'VPC', {
isDefault: true
})
const userData = ec2.UserData.forLinux()
userData.addCommands(
'apt-get update -y',
'apt-get install -y git awscli ec2-instance-connect',
'until git clone https://github.com/aws-quickstart/quickstart-linux-utilities.git; do echo "Retrying"; done',
'cd /quickstart-linux-utilities',
'source quickstart-cfn-tools.source',
'qs_update-os || qs_err',
'qs_bootstrap_pip || qs_err',
'qs_aws-cfn-bootstrap || qs_err',
'mkdir -p /opt/aws/bin',
'ln -s /usr/local/bin/cfn-* /opt/aws/bin/'
)
const machineImage = ec2.MachineImage.fromSSMParameter(
'/aws/service/canonical/ubuntu/server/focal/stable/current/amd64/hvm/ebs-gp2/ami-id',
ec2.OperatingSystemType.LINUX,
userData
)
const myVmSecurityGroup = new ec2.SecurityGroup(this, 'myVmSecurityGroup', {
@loige
Example of a CDK stack (TypeScript)
79

80. An article about CDK (with examples)
@loige
loige.link/cdk-article
80

81. Switch over
@loige
81

82. Switch over
@loige
🙀How do we migrate the data?
😥How do we switch the traffic to the new infrastructure?
82

83. Streamlined data migration
@loige
Update the "old" code-base to save every
new file also to S3.
Copy all the existing file to the S3 bucket
(S3 sync).
83

84. Streamlined data migration
@loige
AWS Database Migration service allows
you to replicate all the data from the old
database to the new one.
It will also keep the 2 Databases in sync
during the switch over!
84

85. Switching traffic
@loige
Request a new certificate using AWS
Certificate Manager (ACM).
Can be validated by email or DNS.
Point your DNS to the new Load Balancer
in AWS!
85

86. WE ARE LIVE! 🎉
@loige
Now what?
86

87. New challenges 🤨
@loige
Observability
Testing
Building & Deployment
87

88. New opportunities 😊
@loige
We can scale dynamically!
As the team grows and the system gets more
complicated we can start to think about micro-
services.
We can start to play with other AWS services (E.g.
SQS + Lambda for background task processing).
88

89. 💸Cost
@loige
89

90. 💸Cost
@loige
calculator.aws/#/estimate?id=1e0779adb67305166c01a583f5d7f61f7c92b029
Load Balancer $ 24.24
EC2 (6 instances) $ 85.87
ElastiCache Redis (3 instances) $ 78.84
RDS PostgreSQL (3 instances) $ 155.48
S3 (1TB) $ 32.55
TOT $ 376.98
90

91. 💸Cost
@loige
Cost estimates are always a bit of a "gamble"...
I selected some arbitrary instance sizes (EC2, RDS, ElastiCache).
I am not accounting for auto-scaling.
I am not accounting for network traffic.
Better to look at cost in production and try to optimise when
needed.
Rule of thumb: try to balance cost with your revenue.
Rule of thumb (2): consider the !
total cost of ownership
91

92. ☐ Create an AWS Account
☐ Select a tool for IaaC
☐ Create and configure a VPC in a region (3 AZs, Public /
Private subnets)
☐ Create an S3 bucket
☐ Update the old codebase to save every new file to S3
☐ Copy all the existing files to S3
☐ Spin up the database in RDS (Multi-AZ)
☐ Migrate the data using Database Migration Service
☐ Provision the ElastiCache Redis Cluster (Multi-AZ)
✏Bonus: a TODO list for the migration
@loige
☐ Create an AMI for the application
☐ Create a security groups and an IAM policy for EC2
☐ Make the application stateless
☐ Create an health check endpoint
☐ Create an autoscaling group to spin up the instances
☐ Create a certificate in ACM
☐ Provision an Application Load Balancer (public subnets)
☐ Configure Https, Targets and Health Checks
☐ Configure Route53
☐ Traffic switch-over through DNS 🤞
📝 Great guide to cloud migrations: 6 strategies for migrating applications to the cloud 92

93. The cloud is a journey
not a destination
The cloud is a journey
not a destination
@loige
93

94. ☝nodejsdp.link
Thank you!
Special thanks to:
, ❤
Photos by
@micktwomey @eoins
Unsplash
@loige
loige.link/mono-lit
94