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microservices architecture
is it the right choice
to design long-living
systems?
Mauro Servienti
mauroservienti

All I wanna do
when I wake up in
the morning is…
Rosanna, Toto. Toto IV
mauroservienti

Buy a "Banana Protector"
mauroservienti

Buy a "Banana Protector"
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Shopping Cart Microservice
[ list-of ]
- Item ID
- Price
- Quantity
- Inventory
- Name
- Description
Shopping Cart
mauroservienti

please, welcome the
business
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Business requirements (#1)
mauroservienti

Products & Shopping Cart Microservices
[ list-of ]
- Item ID
- Price
- Quantity
- Inventory
- Name
- Description
Shopping Cart
- Item ID
- Price
Products
mauroservienti

Products & Shopping Cart Microservices
[ list-of ]
- Item ID
- Price
- Quantity
- Inventory
- Name
- Description
Shopping Cart
- Item ID
- Price
Products
copy
mauroservienti

Business requirements (#2)
mauroservienti

Products & Shopping Cart Microservices
[ list-of ]
- Item ID
- Price
- Quantity
- Inventory
- Name
- Description
Shopping Cart
- Item ID
- Price
- Inventory
Products
mauroservienti

Products & Shopping Cart Microservices
[ list-of ]
- Item ID
- Price
- Quantity
- Inventory
- Name
- Description
Shopping Cart
- Item ID
- Price
- Inventory
Products
copy
copy
mauroservienti

Business requirements (#3)
mauroservienti

Products & Shopping Cart Microservices
[ list-of ]
- Item ID
- Price
- Quantity
- Inventory
- Name
- Description
Shopping Cart
- Item ID
- Price
- Inventory
Products
mauroservienti

Products & Shopping Cart Microservices
[ list-of ]
- Item ID
- CurrentPrice
- LastPrice
- Quantity
- Inventory
- Name
- Description
Shopping Cart
- Item ID
- Price
- Inventory
Products
mauroservienti

Products & Shopping Cart Microservices
[ list-of ]
- Item ID
- CurrentPrice
- LastPrice
- Quantity
- Inventory
- Name
- Description
Shopping Cart
- Item ID
- Price
- Inventory
Products
Is item XYZ in a cart?
Swap & Insert Prices
Move to Saved for…
Update XYZ Price
mauroservienti

service
boundaries
violation
mauroservienti

Price doesn’t feel in the right place
- Item ID
- Price
- Inventory
Products
mauroservienti

ownership
is lost
mauroservienti

Suppliers & Products & Shopping Cart
[ list-of ]
- Item ID
- CurrentPrice
- LastPrice
- Quantity
- Inventory
- Name
- Description
Shopping Cart
- Item ID
- Price
- Inventory
Products
Is item XYZ in a cart?
Swap & Insert Prices
Move to Saved for…
- Supplier ID
- Item ID
- Purchase Price
Suppliers
Update XYZ Price
Are we selling?
New Purchase Price
mauroservienti

autonomy?
puff, it’s gone
mauroservienti

HTTP all the rage
because it’s the microservices way
mauroservienti

Suppliers & Products & Shopping Cart
[ list-of ]
- Item ID
- CurrentPrice
- LastPrice
- Quantity
- Inventory
- Name
- Description
Shopping Cart
- Item ID
- Price
- Inventory
Products
Is item XYZ in a cart?
Swap & Insert Prices
Move to Saved for…
- Supplier ID
- Item ID
- Purchase Price
Suppliers
Update XYZ Price
Are we selling?
New Purchase Price
mauroservienti

“the microservices way”
Shopping CartProducts
Is item XYZ in a cart?
Swap & Insert Prices
Move to Saved for…
Suppliers Update XYZ Price
Are we selling?
New Purchase Price
• Incoming “external” HTTP Post
• HTTP Query from Suppliers to Products
• HTTP Post from Suppliers to Products
• HTTP Query from Products to Shopping Cart
• HTTP Post from Products to Shopping Cart
mauroservienti

The snowball effect
[ list-of ]
- Item ID
- CurrentPrice
- LastPrice
- Quantity
- Inventory
- Name
- Description
Shopping Cart
- Item ID
- Price
- Inventory
Products
Is item XYZ in a cart?
Swap & Insert Prices
Move to Saved for…
- Supplier ID
- Item ID
- Purchase Price
Suppliers
Update XYZ Price
Are we selling?
New Purchase Price Ooops...
mauroservienti

temporal
coupling
anyone?
mauroservienti

The snowball effect: can we rollback?
[ list-of ]
- Item ID
- CurrentPrice
- LastPrice
- Quantity
- Inventory
- Name
- Description
Shopping Cart
- Item ID
- Price
- Inventory
Products
Is item XYZ in a cart?
Swap & Insert Prices
Move to Saved for…
- Supplier ID
- Item ID
- Purchase Price
Suppliers
Update XYZ Price
Are we selling?
New Purchase Price Ooops...
mauroservienti

distributed
transactions
over HTTP
mauroservienti

mauroservienti

Messaging
temporal coupling and
distributed transactions
mauroservienti

The snowball effect
[ list-of ]
- Item ID
- CurrentPrice
- LastPrice
- Quantity
- Inventory
- Name
- Description
Shopping Cart
- Item ID
- Price
- Inventory
Products
Is item XYZ in a cart?
Swap & Insert Prices
Move to Saved for…
- Supplier ID
- Item ID
- Purchase Price
Suppliers
Update XYZ Price
Are we selling?
New Purchase Price Ooops...
mauroservienti

The snowball effect
[ list-of ]
- Item ID
- CurrentPrice
- LastPrice
- Quantity
- Inventory
- Name
- Description
Shopping Cart
- Item ID
- Price
- Inventory
Products
- Supplier ID
- Item ID
- Purchase Price
Suppliers
New Purchase Price
+ new price details
Business
Logic
Purchase Price Changed
+ new price details
Business
Logic
Sell Price Changed
MovetoSavedfor…
mauroservienti

The snowball effect
[ list-of ]
- Item ID
- CurrentPrice
- LastPrice
- Quantity
- Inventory
- Name
- Description
Shopping Cart
+ new price details
Business
Logic
Sell Price Changed
MovetoSavedfor…
Ooops...
mauroservienti

palliative
alleviates the symptoms
mauroservienti

Queries are still a thing: Add item to cart.
[ list-of ]
- Item ID
- Price
- Quantity
- Inventory
- Name
- Description
Shopping Cart
- Item ID
- Price
- Inventory
Products
copy price
copy inventory
mauroservienti

Data sharing is still a thing
[ list-of ]
- Item ID
- CurrentPrice
- LastPrice
- Quantity
- Inventory
- Name
- Description
Shopping Cart
+ new price details
Business
Logic
Sell Price Changed
MovetoSavedfor…
mauroservienti

We’re flooding the system…
Shopping CartProducts
Is item XYZ in a cart?
Swap & Insert Prices
Move to Saved for…
Is item XYZ in a cart?
Update XYZ inventory
Is item XYZ in a cart?
Swap & Insert Prices
Move to Saved for…
Is item XYZ in a cart?
Update XYZ inventory
Is item XYZ in a cart?
Swap & Insert Prices
Move to Saved for…
Is item XYZ in a cart?
Update XYZ inventory
Is item XYZ in a cart?
Swap & Insert Prices
Move to Saved for…
Is item XYZ in a cart?
Update XYZ inventory
Is item XYZ in a cart?
Swap & Insert Prices
Move to Saved for…
Is item XYZ in a cart?
Update XYZ inventory
Is item XYZ in a cart?
Swap & Insert Prices
Move to Saved for…
Is item XYZ in a cart?
Update XYZ inventory
Is item XYZ in a cart?
Swap & Insert Prices
Move to Saved for…
Is item XYZ in a cart?
Update XYZ inventory
Is item XYZ in a cart?
Swap & Insert Prices
Move to Saved for…
Is item XYZ in a cart?
Update XYZ inventory
Is item XYZ in a cart?
Swap & Insert Prices
Move to Saved for…
Is item XYZ in a cart?
Update XYZ inventory
Is item XYZ in a cart?
Swap & Insert Prices
Move to Saved for…
Is item XYZ in a cart?
Update XYZ inventory
Is item XYZ in a cart?
Swap & Insert Prices
Move to Saved for…
Is item XYZ in a cart?
Update XYZ inventory
Is item XYZ in a cart?
Swap & Insert Prices
Move to Saved for…
Is item XYZ in a cart?
Update XYZ inventory
Update XYZ Price
Update XYZ Inventory
Over and over, and over, and over…
mauroservienti

http://montages.no/2009/09/begrepet-grafisk-likhet/ mauroservienti

User mental model is misleading
[ list-of ]
- Item ID
- CurrentPrice
- LastPrice
- Quantity
- Inventory
- Name
- Description
Shopping Cart
- Item ID
- Price
- Inventory
Products
- Supplier ID
- Item ID
- Purchase Price
Suppliers
mauroservienti

Let’s focus on the Shopping Cart
[ list-of ]
- Item ID
- CurrentPrice
- LastPrice
- Quantity
- Inventory
- Name
- Description
- Etc…
Shopping Cart
mauroservienti

Sales shopping cart
[ list-of ]
- Item ID
- Quantity
- Inventory
- Name
- Description
- Delivery Est.
Shopping Cart
- Item ID
- Price
Sales
[ list-of ]
- Item ID
- CurrentPrice
- LastPrice
- Quantity
mauroservienti

- Item ID
- Price
Sales
[ list-of ]
- Item ID
- CurrentPrice
- LastPrice
- Quantity
Warehouse shopping cart
[ list-of ]
- Item ID
- Quantity
- Name
- Description
- Delivery Est.
Shopping Cart
[ list-of ]
- Cart ID
- Item ID
- Inventory
- Quantity
Warehouse
- Item ID
- Inventory
mauroservienti

Shipping shopping cart
[ list-of ]
- Item ID
- Quantity
- Name
- Description
Shopping Cart
[ list-of ]
- Cart ID
- Item ID
- Quantity
- Delivery Est.
- Item ID
- Price
Sales
[ list-of ]
- Item ID
- CurrentPrice
- LastPrice
- Quantity
[ list-of ]
- Cart ID
- Item ID
- Inventory
- Quantity
Warehouse
- Item ID
- Inventory
- Item ID
- Delivery
Type
Shipping
mauroservienti

Marketing tends to be stable
[ list-of ]
- Item ID
- Quantity
Shopping Cart
[ list-of ]
- Cart ID
- Item ID
- Quantity
- Delivery Est.
- Item ID
- Price
- Item ID
- Name
- Description
Marketing
Sales
[ list-of ]
- Item ID
- CurrentPrice
- LastPrice
- Quantity
[ list-of ]
- Cart ID
- Item ID
- Inventory
- Quantity
Warehouse
- Item ID
- Inventory
- Item ID
- Delivery
Type
Shipping
mauroservienti

Do we need the Shopping Cart at all?
[ list-of ]
- Item ID
- Quantity
Shopping Cart
[ list-of ]
- Cart ID
- Item ID
- Quantity
- Delivery Est.
- Item ID
- Price
- Item ID
- Name
- Description
Marketing
Sales
[ list-of ]
- Item ID
- CurrentPrice
- LastPrice
- Quantity
[ list-of ]
- Cart ID
- Item ID
- Inventory
- Quantity
Warehouse
- Item ID
- Inventory
- Item ID
- Delivery
Type
Shipping
mauroservienti

Can Sales be responsible for that concept?
[ list-of ]
- Cart ID
- Item ID
- Quantity
- Delivery Est.
- Item ID
- Price
- Item ID
- Name
- Description
Marketing
Sales
Cart ID
[ list-of ]
- Item ID
- CurrentPrice
- LastPrice
- Quantity
[ list-of ]
- Cart ID
- Item ID
- Inventory
- Quantity
Warehouse
- Item ID
- Inventory
- Item ID
- Delivery
Type
Shipping
mauroservienti

We followed the coupling
[ list-of ]
- Cart ID
- Item ID
- Quantity
- Delivery Est.
- Item ID
- Price
- Item ID
- Name
- Description
Marketing
Sales
Cart ID
[ list-of ]
- Item ID
- CurrentPrice
- LastPrice
- Quantity
[ list-of ]
- Cart ID
- Item ID
- Inventory
- Quantity
Warehouse
- Item ID
- Inventory
- Item ID
- Delivery
Type
Shipping
mauroservienti

What a (micro)service is
the technical authority
for a specific business
capability
All business rules (& data) reside within the service
mauroservienti

Full Vertical Slices
MarketingSales Warehouse Shipping
behavior & databehavior & data behavior & databehavior & data
mauroservienti

Full Vertical Slices
MarketingSales Warehouse Shipping
behavior & databehavior & data behavior & databehavior & data
UI & ViewModel
Composition
UI & ViewModel
Composition
UI & ViewModel
Composition
UI & ViewModel
Composition
mauroservienti

Full Vertical Slices
MarketingSales Warehouse Shipping
behavior & databehavior & data behavior & databehavior & data
UI & ViewModel
Composition
UI & ViewModel
Composition
UI & ViewModel
Composition
UI & ViewModel
Composition
Dedicated
Technology / FX
Dedicated
Technology / FX
Dedicated
Technology / FX
Dedicated
Technology / FX
mauroservienti

time tyranny
Demo
bit.ly/codemotion-webinar-microservices
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Takeaways
• Boundaries are key to success
• Do not bring in more technology to solve non-
technical problems
mauroservienti

Takeaways
• Boundaries are key to success
• Mental model can badly influence design
• Users/Business analysts tend to think in term
of data presentation
mauroservienti

Takeaways
• Boundaries are key to success
• Mental model can badly influence design
• Do not name things prematurely
• Premature names stick and drive data
aggregation
mauroservienti

Takeaways
• Boundaries are key to success
• Mental model can badly influence design
• Do not name things prematurely
• Behaviors define how to aggregate data
• Group data that change together and that influence each
other
• Use anti-requirements techniques to validate data
grouping
• Follow the coupling
mauroservienti

Takeaways
• Boundaries are key to success
• Mental model can badly influence design
• Do not name things prematurely
• Behaviors define how to aggregate data
• Use messaging to temporally decouple services
mauroservienti

ViewModel Composition
//milestone.topics.it

you don’t need a distributed system
first rule of distributed systems
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Q&A
Thank you!
mauroservienti