Legacy systems are the kings of our IT architecture. They rule the evolution of the technology ecosystem that hosts them thanks to the control they have acquired over time on core data and key business processes. Legacy systems however pose severe limits in addressing critical business needs, as well as seizing opportunities for future growth. Digital Integration Hub (DIH) is a quite popular architecture to modernize legacy systems allowing the IT to evolve faster and better integrate modern technologies. In this talk we’ll: - Review DIH general architecture - Illustrate different patterns to offload data from legacy systems to Kafka with pros and cons in term of consistency and latency - Present different ways to consume data offloaded from legacy system to Kafka and their fit with different use cases - Show how to close the loop and use Kafka and CQRS pattern to handle all the data moving backward from applications to legacy systems

1. KAFKA Summit EMEA 2021
Andrea Gioia
CTO at Quantyca
Co-Founder at Blindata
From legacy systems to microservices and back

2. What is legacy modernization
Current integration architecture between frontend
applications and backend legacy systems does not
scale anymore
The legacy systems cannot be replaced overnight
A better integration architecture is needed in order to
modernize them in place.
...and why it matters
System of Engagement System of Insight
System of Records
Legacy
Systems
Application
Layer
Integration
Layer
Point to point “Spaghetti” integration

3. Who am I?
Not an easy question to answer but keeping it simple...
Andrea Gioia
andrea.gioia@quantyca.it
Quantyca is a privately owned technological
consulting firm specialized in data and metadata
management based in Italy
quantyca.it
Blindata is a SAAS platform that leverages Data
Governance and Compliance to empower your
Data Management projects.
blindata.io
CTO
CO-FOUNDER

4. Integration architecture #1
All new functionalities are implemented directly by extending
the legacy system or by buying complementary products
offered by the same vendor of the legacy system.
Integration layer if present is limited to an API Gateway to
decouple legacy backend from frontend applications
Legacy systems take it all
System of Engagement
Frontend
System of Insight
Frontend
System of Records
Legacy
Systems
Application
Layer
Integration
Layer
API Gateway
SoE
&
SoI
Backend
SoE
&
SoI
Backend
SoE
&
SoI
Backend
SoE
&
SoI
Backend
SoE
&
SoI
Backend
TIME-TO-MARKET AND BUSINESS AGILITY
IMPROVEMENT
COSTS AND RISKS REDUCTION
RESILIENCE AND PERFORMANCE
IMPROVEMENT

5. Integration architecture #2
Integration rationalization through composite services
System of engagement System Of Insight
System of Records
Legacy
Systems
Application
Layer
Integration
Platform
API Gateway
Request Based Integration Layer
Application Services
Process Services
Sourcing Services
Composite Services
Integrations are rationalized through different layers of
reusable and composable services.
Sourcing services wrap legacy systems, process service
orchestrate business process and application services
provide a backend for frontend applications
TIME-TO-MARKET AND BUSINESS AGILITY
IMPROVEMENT
COSTS AND RISKS REDUCTION
RESILIENCE AND PERFORMANCE
IMPROVEMENT

6. Integration architecture #2
Integration rationalization through data virtualization
System of engagement System Of Insight
System of Records
Legacy
Systems
Application
Layer
Integration
Platform
API Gateway
Request Based Integration Layer
Application Layer
Business Layer
Physical Layer
Virtual DWH
TIME-TO-MARKET AND BUSINESS AGILITY
IMPROVEMENT
COSTS AND RISKS REDUCTION
RESILIENCE AND PERFORMANCE
IMPROVEMENT
Integrations are rationalized through different layers of
views served by a data virtualization application.
Physical layer wraps legacy systems, business layer
exposes the business model and application layer provide
projections designed to facilitate consumption.

7. Integration architecture #2
Integration rationalization
System of engagement System Of Insight
System of Records
Legacy
Systems
Application
Layer
Hybrid
Integration
Platform
API Gateway
Request Based Integration Layer
Virtual DWH
Composite Services
TIME-TO-MARKET AND BUSINESS AGILITY
IMPROVEMENT
COSTS AND RISKS REDUCTION
RESILIENCE AND PERFORMANCE
IMPROVEMENT
Composite services and data virtualization can be used in the
same architecture. The former is preferred to back system of
engagement the latter to back system of insight.
Both solutions simplify integrations but don’t reduce the
workload on the backend systems

8. Integration architecture #3
Data offloading
System of engagement System Of Insight
System of Records
Legacy
Systems
Application
Layer
Hybrid
Integration
Platform
API Gateway
Event-BasedIntegration Layer
High-Performance Data Store
Microservices
Metadata Management
TIME-TO-MARKET AND BUSINESS AGILITY
IMPROVEMENT
COSTS AND RISKS REDUCTION
RESILIENCE AND PERFORMANCE
IMPROVEMENT
Data offloaded from legacy systems are aggregated into low-
latency, high performance datastore accessible via APIs,
events or batch.
The data store synchronizes with the beck ends via event-
driven integration patterns.

9. Digital Integration Hub
Key building blocks
Event store
High
performanc
e data store
Connectors
Legacy
Systems Applications
Services
Where the data is
stored
Keeps the legacy
systems and the high
performance data
store in sync
offloading all
modifications to
relevant data in real
time
Transform technical
events coming from
connectors to
domain and business
events that can be
consumed
downstream by high
performance data
store or other
consumers (event
driven integration)
Stores domain
specific data
exposing a single
consolidated view of
entities
~
Supports fast
ingestion to reduce
eventual consistency
window
~
Can support
analytical queries
Connect to high
performance data
store for read queries
Execute write on the
legacy systems by
means of command
events pushed on the
event store
(command query
responsibility
segregation)
Where the data is
used

10. Legacy System Streaming Platform
Connectors
Data acquisition patterns

11. Legacy System Streaming Platform
Technical
Events
(Speed &
Fidelity)
Domain
Events
(Trusted
Views)
Business
Events
(Ease of
consumption)
Event Store
Event driven integration

12. Legacy System Streaming Platform
Technical
Events
(Speed &
Fidelity)
Domain
Events
(Trusted
Views)
High
Performance
Data Store
Business
Events
(Ease of
consumption)
High-performance data store
Some options

13. Legacy System Streaming Platform
Technical
Events
(Speed &
Fidelity)
Domain
Events
(Trusted
Views)
High
Performance
Data Store
Business
Events
(Ease of
consumption)
Commands
Micro/Mini
Services
READ
WRITE
Microservices
From legacy systems to services and back

14. The legacy modernization journey
Offloading, Isolation and Refactoring
Legacy System
Digital
Integration Hub
Applications
1
Legacy
Offloading
Legacy System
Digital
Integration Hub
Applications
Anti Corruption
Layer
Bubble Context
2
Legacy
Isolation
Digital
Integration Hub
Applications
Anti Corruption
Layer
Bubble Context
3
Legacy
Refactoring

15. Takeaways
Digital integration hub can be seen as a way of decoupling systems using data as anti corruption layer. Data offloaded into the
integration platform become a first-class citizen of the new data centric architecture.
Benefits
○ Responsive user experience
○ Offload legacy systems from expansive workloads
generated by front-end services
○ Support legacy refactoring
○ Align services to business domain
○ Enable real time analytics
○ Foster a data centric approach to integration
Challenges
○ Adapting the conceptual architecture to your
specific context
○ Assembling different technology components,
possibly from different vendors
○ Operating a complex distributed and loosely coupled
architecture
○ Supporting bidirectional synchronization
○ Designing the domain data models for the business
entities
○ Developing services that can tolerate eventual
consistency
○ Managing organizational politics related to data
ownership

16. Questions?
Feel free to ask
andrea.gioia@quantyca.it