The document discusses techniques for modernizing legacy systems, including digital decoupling. Digital decoupling aims to isolate legacy systems to break the cycle of increasing costs when adding features. It unlocks constrained legacy data and delivers new business value on a modern cloud architecture. This allows replacing the core systems over time while continuously delivering value. The key techniques discussed are using microservices, change data capture, event-driven architectures, and domain-driven design to begin digitally decoupling legacy systems.

1. Getting Microservices and
Legacy to Play Nicely
Together with Event-Driven
Architectures
October 9, 2019
Austin Convention Center

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Why does modernization
often cost so much?
2

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TOO MUCH TECHNOLOGY
DEBT
Why does modernization
often cost so much?
3

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The legacy paradox
Technical debt in our legacy
systems severely limits our IT
function’s ability to be innovative
Technical debt in our
legacy systems
increases our IT Costs
The Good, … The Bad … and, The Ugly
Source: Accenture Research Digital Decoupling Survey, July 2018
Our legacy systems contain
trapped value that can be used
for innovation
4

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What are some techniques
for modernization?
5

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We could use a code translation tool
And transmogrify it.
Code Generation Tools
6

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We could build a new system to replace it.
7

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We could containerize it.
8

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We could use microservices in the cloud…
Micro-
service
A
Micro-
service
B
9

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…and “just” replace pieces of it
Micro-
service
A
New
API
Layer Call APIs to Synchronize
Micro-
service
B
Retire
10

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DIGITAL
DECOUPLING
Change the business…
while running the business
11

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We can have old and new, at the same
time
Micro-serv
ice
A
New
API
Layer Call APIs to Synchronize
Pub-Sub to Synchronize
Change
Data
Capture
Micro-serv
ice
B
12

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Pivoting to new while leveraging the good in
Legacy
Fundamentally, Digital Decoupling is a new
methodology to:
1. Isolate legacy systems so as to break the cycle of
multiplicative cost when adding or integrating features.
2. Unlock the data that has been constrained by the legacy
systems and make it accessible.
3. Deliver new business value on top of a modern, cloud
native architecture capable of delivering new products
quickly.
4. Hollow out and replace the core gradually over time,
ending with new systems within similar timelines to the old
transformations, but with far more value delivered along
the way.
13

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Domain APIs
14
Legacy / package / SaaS Domain Microservice
Engagement Channels
Event Hub
Legacy / Package /
SaaS
New Decoupling
Components
Channels
Legacy /
Package /
SaaS
System
REST Endpoints
Data flow
Event
Consumer
Domain DB
Event
Producer
Web
Service(s)
Event
Consumer
Event
Consumer
Specialized View
REST Endpoints
Event
Consumer
DB /
In-Memor
y
Data Lake
Reporting &
Insights API
ViewViewData
Stores
Event
Consumer
Legacy
DB
Transformer
Event
Consumer
/ Producer
CDC
Event
Consumer
Insights
Engagement Service
DB /
In-Memor
y
Engagement APIs
Digital Decoupling Pattern

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Change Data
Capture (CDC)
Event-Driven
Architecture / Event
Streaming
Microservices
15
The Building Blocks

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Begin the journey to digital decoupling
1. Use domain driven design and build
microservices
2. Build a proof of architecture
3. Performance test it
4. Keep it simple
5. Be mindful of where the data is