The Rise of Reactive Microservices

WeAreDevelopers 2022 — Berlin
@duffleit

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David Leitner
@duffleit
Coding Architect
[email protected]
@duﬄeit

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@duffleit
Somewhen in 2011.

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@duffleit
User

Account

Legder

WebBanking
New Payment
💸
Perform Payment
€ 20, 00
👧
Lisa
to
David
from
transferMoney
triggerPayment
createTransactions

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@duffleit
User

Account

Legder

WebBanking
Your payment was
successfully executed.
transferMoney
triggerPayment
createTransactions
✅

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@duffleit
User

Account

Legder

WebBanking
New Payment
💸
Perform Payment
€ 20, 00
👧
Lisa
to
David
from
transferMoney
triggerPayment
createTransactions
Legder
Legder

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@duffleit
User

Account

Legder

WebBanking
Your payment was
successfully executed.
transferMoney
triggerPayment
createTransactions
✅
Retries
Timeouts
Circuit Breakers
Synchronise

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First Generation of MicroServices
Synchronously Integrated
@duffleit

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@duffleit
User

Account

WebBanking
transferMoney
triggerPayment
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment

Legder

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@duffleit
User

Account

WebBanking
transferMoney
triggerPayment
createTransactions
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Queue

Legder

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@duffleit
User

Account

WebBanking
transferMoney
triggerPayment
createTransactions Queue

Legder
Your payment was
accepted.
✅

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@duffleit
User

Account

WebBanking
transferMoney
triggerPayment

Legder
Your payment was
accepted.
✅
Legder

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@duffleit
User

Account

WebBanking
transferMoney
triggerPayment

Legder
Your payment was
accepted.
✅
Legder

Queue

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@duffleit
User

Account

WebBanking
transferMoney
triggerPayment

Legder
Your payment was
accepted.
✅
Legder

Queue
Queue

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Second Generation of MicroServices
Message-Driven and Asynchronously
Integrated
@duffleit

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@duffleit
User

Account

WebBanking
transferMoney
triggerPayment
createTransactions
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Legder

Queue
Queue
Queue

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@duffleit
User

Account

WebBanking
transferMoney
triggerPayment
createTransactions
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Legder

Queue
Queue
Queue
As a Customer, I want my
transaction to be booked
by the ledger.

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@duffleit
User

Account

WebBanking
transferMoney
triggerPayment
createTransactions
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Legder

Queue
Queue
Queue
As a Customer, I want the
account service to update
my balance.

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@duffleit
User

Account

WebBanking
transferMoney
triggerPayment
createTransactions
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Legder

Queue
Queue
Queue
As a Customer, I want
to transfer money to
someone else.

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The Entity Service
Antipattern.
@duffleit

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Let's create Services along
Customer Journeys.
@duffleit

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@duffleit
“ On the Criteria To Be Used in
Decomposing Systems into Modules
— Parnas, 1972

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Let's create Services along
Customer Journeys.
@duffleit

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@duffleit
User

Account

WebBanking
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Legder

Payments

Domain Services
Journey Services
someone else.

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@duffleit
User

Account

WebBanking
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Legder

Web-BFF

Domain Services
Backend For Frontends
someone else.
Mobile-BFF

Mobile Banking
€ 20, 00
Pay
Payment Flow
Payment Flow

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@duffleit
No Domain Logic in
Backend For Frontends.
It's about Ui-Speciﬁc Aggregation, to get rid
of over-fetching and over-requesting.

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@duffleit
User

Account

WebBanking
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Legder

Payments

Domain Services
Journey Services

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@duffleit
User

Account

WebBanking
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Legder

Payments

Domain Services
Journey Services
Balance

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@duffleit
⚡
Customer Journey & Entity Data
Mismatch Problem

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@duffleit
Users Accounts Transactions
Entities
Customer Journeys
Payments
Onboarding
Fraud Detection
⚡

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@duffleit
User Account
WebBanking
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Transactions
Payments
Domain Services
Journey Services
Onboarding Fraud Detection
User Account
Account Transactions

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@duffleit
User Account
WebBanking
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Transactions
Payments
Domain Services
Journey Services
User Account
⚡
⚡ ⚡

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@duffleit
WebBanking
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Payments
Journey Services
User Account
User
Account
Transactions
Service Autnomy

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@duffleit
WebBanking
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Payments
Journey Services
User Account
User
Account
Transactions
Data Duplication
⚡

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@duffleit
WebBanking
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Payments
Journey Services
User Account
User
Account
Transactions
Data Syncronisation
🤯
⚡

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@duffleit
clarify who owns which Data.
Always

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@duffleit
WebBanking
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Payments
Journey Services
User Account
User
Account
Transactions

View Slide

@duffleit
WebBanking
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Payments
Journey Services
User
Account
Account
Transactions
User
Account
Transactions
Synchronous Calls
😔

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@duffleit
WebBanking
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Payments
Journey Services
User
Account
Account
Transactions
User Cache
Account
Transactions
Synchronous Calls
😔

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@duffleit
There must be a better solution
🤔

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@duffleit
🤔
Payments
User
Onboarding
User
pull

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@duffleit
🤔
Payments
User
Onboarding
User
push

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@duffleit
Payments
Onboarding
User Aggregate User Readmodel
UserChangedEvent
UserChange
Command
That's CQRS in a nutshell
🥜
update

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@duffleit
Payments
Onboarding
UserChangedEvent
UserChange
Command
Stream

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@duffleit
Payments
Onboarding
UserChange
Command
Stream
UserChangedEvent
transform
apply

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@duffleit
WebBanking
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Payments
Journey Services
User
Account
Account
Transactions
User
Account
Transactions
Stream

View Slide

@duffleit
WebBanking
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Payments
Journey Services
User
Account
Account
Transactions
User
Account
Transactions
Stream
Projections

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@duffleit
WebBanking
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Payments
Journey Services
User
Account
Account
Transactions
User
Account
Transactions
Stream

View Slide

@duffleit
WebBanking
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Payments
Journey Services
User
Account
Account
Transactions
User
Account
Transactions
Stream
Projections

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@duffleit
But didn't we just introduce
Eventual Consistency?

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@duffleit
The diﬀerent faces of
Eventual Consistency

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@duffleit
Eventual Divergence
Dashboard
User (age: 22)
UserChanged (age: 21)
UserChanged (age: 22)
Proﬁle
User (age: 21)
⚡
timestamp
timestamp

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@duffleit
Eventual Divergence
Eventual Variance
Ledger
Stream
Transaction (+10€)
🔥

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@duffleit
Eventual Divergence
Eventual Variance
Ledger
Dashboard
Stream
🔥 Transaction (+10€) Transaction (+10€)
Balance: 20€

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@duffleit
Eventual Divergence
Eventual Variance
Eventual Latency
Service B
Stream
UserChanged (age: 21) UserChanged (age: 22)
Proﬁle
User (age: 21)
Dashboard
User (age: 21)
User (age: 22)

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Single User Context
@duffleit
Eventual Divergence
Eventual Variance
Eventual Latency
Service B
Stream
UserChanged (age: 21) UserChanged (age: 22)
Proﬁle
User (age: 21)
Dashboard
User (age: 21)
User (age: 22)
🕰

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@duffleit
Eventual Divergence
Eventual Variance
Eventual Latency
same events, different results.
same events, different quantity.
same events, different realisation.
Ordering Guarantees
Optimistic UIs
At-Least-Once
Delivery
Deduplication
Mechanisms

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@duffleit
tl/dr:
Eventual Consistency is
often used as a
knock-out argument
@duffleit

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@duffleit
tl/dr:
Eventual Consistency is
often used as a
knock-out argument
but isn't, in most cases.
@duffleit

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@duffleit
WebBanking
New Payment
💸
€ 20, 00
👧
Lisa
to
David
from
Perform Payment
Payments
Journey Services
User
Account
Account
Transactions
User
Account
Transactions
Stream
Projections

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@duffleit
Mobile Banking Usage
93% — Show balance & last transactions
3% — Initiate new payment
4% — Any other functionality

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@duffleit
Payments
Journey Services
Onboarding Overview
User
Account
Account
Transactions
User
Account
Transactions
Stream

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@duffleit
Payments
Journey Services
Onboarding Overview
User
Account
Account
Transactions
User
Account
Transactions
Stream
93% of what our users need
can still be performed.
WebBanking
Current Balance: 200€
👧
You sent Lisa 100€
Christoph sent you 300€

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@duffleit
WebBanking
👧
You sent Lisa 100€
Payments
Journey Services
Onboarding Overview
User Account
Transactions
User
Account
Transactions
Stream
Overview
Transactions
We can easily scale
horizontally.

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@duffleit
WebBanking of David
Payments
Journey Services
Onboarding Overview
User Account
Transactions
User
Account
Transactions
Stream
WebBanking of Lisa
👧
New Payment
💸
€ 20, 00 David
to
👧
Lisa
from
Perform Payment

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@duffleit
WebBanking of David
Payments
Journey Services
Onboarding Overview
User Account
Transactions
User
Account
Transactions
Stream
WebBanking of Lisa
👧
New Payment
💸
€ 20, 00 David
to
👧
Lisa
from
Perform Payment
👧
Lisa sent you 20€

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@duffleit
WebBanking of David
Payments
Journey Services
Onboarding Overview
User Account
Transactions
User
Account
Transactions
Stream
WebBanking of Lisa
👧
New Payment
💸
€ 20, 00 David
to
👧
Lisa
from
Perform Payment
👧
Lisa sent you 20€
GraphQL
subscriptions
mutations
Out-of-the-box
real-time
capabilities.

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@duffleit
WebBanking of David
Payments
Journey Services
Legacy System
Accounts
Stream
👧
Lisa sent you 20€
User
😮 💨😮 💨
😮 💨
Change Data
Capture (CDC) User User

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Third Generation of MicroServices
Built on Reactive Data-Streams
@duffleit
High Resilience
🔥
Horizontal Scaling ↔
Real Time Integration
⏱
Good Integration with Legacy Systems
🏚

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Dimensions of Scaling
@duffleit
Vertical
Horizontal
Service

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Vertical
Horizontal
Service Service' Service''
Stream

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Vertical
Horizontal
Service Service' Service''
Sharding

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Vertical
Horizontal
Service
Service'
Service''
Sharding
Users A-H
Users I-P
Users Q-Z

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Vertical
Horizontal
Service
Service'
Service''
User from
User from
Users from
Service Service
Service
Sharding

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@duffleit
UserTriggeredPayment

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@duffleit
Stream
UserTriggeredPayment Partition 0 Partition 1 Partition 2

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@duffleit
Stream
Payments Payments Payments

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@duffleit
Stream
ValidPaymentReceived

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@duffleit
Stream
Stream
Partition 0 Partition 1 Partition 2

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Fraud Detection Fraud Detection
@duffleit
Stream
Stream
Fraud Detection
PaymentCheckedAgainstFraud

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@duffleit
Stream
Stream
Fraud Detection
Stream
PaymentChecked

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@duffleit
Stream
Stream
Fraud Detection
Stream
PaymentChecked
Ledger Ledger Ledger
TransactionBooked

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@duffleit
Stream
Stream
Fraud Detection
Stream
PaymentChecked
Stream
TransactionBooked

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@duffleit
Stream
Stream
Fraud Detection
Projecting
Transactions
Streams
Flink
Stream
PaymentChecked
Stream
TransactionBooked
Independent Shards

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@duffleit
Stream
Stream
Fraud Detection
Stream
PaymentChecked
Stream
TransactionBooked
Shard 0 Shard 1 Shard 2
DataSink
Streams
Flink
Projecting
Transactions
WebBanking WebBanking WebBanking

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@duffleit
Stream
Stream
Fraud Detection
Stream
PaymentChecked
Stream
TransactionBooked
Shard 0 Shard 1 Shard 2
DataSink
🚀 We can scale
nearly unlimited.
Projecting
Transactions
WebBanking WebBanking WebBanking

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Forth Generation of MicroServices
Shared and fully Stream Based
@duffleit
Massive Throughput
🚀
Extremely Scalable ↔

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So many choices,
Lets sum up.
@duffleit

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Monolith
@duffleit

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Syncronously
😩 Pain
@duffleit

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Modulith
@duffleit

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Asyncronously
📦 Shared Data
@duffleit

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Reactive
⚡ From Pull to Push
@duffleit

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Streaming Massiv Throughput
🚀
@duffleit

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Monolith Reactive
Push-Based
Async
Pull-Based
Streamed
Availability
🟢
, Resilience
🦺
, Scalability ↔ , Throughput
🚀
Complexity
💰
@duffleit
The Rise of Reactive Microservices.
And the future of fully Stream Based Architectures.

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David Leitner
@duffleit
Coding Architect
[email protected]
@duﬄeit

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squer.link /
slicing-microservices

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The Rise of Reactive Microservices

The Rise of Reactive Microservices

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