The document discusses moving from "fat applications" with monolithic codebases to microservices-based "fit and sexy applications." It notes that fat applications are difficult to maintain and scale, while microservices break applications into independent, loosely coupled components that communicate over well-defined interfaces. This allows individual services to be developed, deployed, and scaled independently. However, the document also cautions that microservices require careful planning and management of coordination, deployment, and other issues. It provides a four-step "diet plan" for decomposing a fat application into initial independent microservices focusing on business capabilities and dependencies.

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MicroServices
A diet for fat applications
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1- Fat Applications
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1- Fat Applications
● One single big fat source code
● Front-end and Back-end are combined
● Each developer clones the complete source code in order
to work
● Difficult to maintain, hundreds of classes, packages and
libraries
● New Developers: “This is fat and scary!”
● => lower productivity and higher frustration
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WAR/EAR
UI Business Logic
BMI over 30!
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1- Fat Applications
● As the number of users/customers increase, scaling is
difficult
● Usual solution is to scale up, get a better hardware
● If there’s a small bug, the whole application is taken
down, a new deploy is required
● Upgrading language/framework or application server is
difficult
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2- Fit & Sexy Applications
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2- Fit & Sexy Applications
● Decomposition of the application into smaller pieces
● Each piece can function on its own. Exclusive business
capability
● Communication between pieces via well-defined interfaces
(HTTP/REST) - Always Stateless
● Independent life cycle (development teams, technology
choices, not held back by other pieces)
● ⇒ Loosely Coupled system, if one piece is dead, the
system isn’t dead
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UI
Students
Classes
Teachers
Salaries
HTTP/REST
HTTP/REST
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2- Fit & Sexy Applications
● Instead of scaling the entire application, scale only the
microservice with higher traffic
● Ready for the cloud
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3- Beauty ain’t always perfect
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3- Beauty ain’t always perfect
● Management
● Maintenance
● Deployment
● Coordination
● System Design
=> Careful planning is required, usage of tools and services
such as containers, VMs, cloud services, etc…
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4- Diet Plan
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4- Diet Plan
● Focus primarily on business when decomposing the fat
application
● Begin with the parts that has the least or none
dependencies
● Only use HTTP (REST/SOAP) and keep it stateless
● Separate the UI
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5- Conclusion
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5- Conclusion
● Having a healthy lifestyle should be our number one
priority
● As obesity is on the rise, it is crucial to stick to a
healthy diet plan
● Being fit, helps us move easier and remain attractive
● Being fat, increases the risks of health problems
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