Microservices, Boounded Contexts, and Everything in Between

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vladikk doit-intl.com MICROSERVICES BOUNDED CONTEXTS AND EVERYTHING IN BETWEEN

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vladikk doit-intl.com ”95% of the words are spent extolling the benefits of “modularity” and that little, if anything, is said about how to achieve it” Glenford J. Myers

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vladikk doit-intl.com

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vladikk doit-intl.com “MICROSERVICES FTW!!!!!!!!1” Me @ Internovus

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vladikk doit-intl.com “MICROSERVICES FTW!!!!!!!!1” Me @ Internovus

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vladikk doit-intl.com ”95% of the words are spent extolling the benefits of “modularity” and that little, if anything, is said about how to achieve it” Glenford J. Myers

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vladikk doit-intl.com Decomposi)on Strategies Microservices Design Heuris)cs

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vladikk doit-intl.com Decomposi)on Strategies Microservices Design Heuris)cs

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vladikk doit-intl.com Decomposi)on Strategies Microservices Design Heuris)cs

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vladikk doit-intl.com INTERNOVUS 01 BUSINESS DOMAIN

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vladikk doit-intl.com Your Product Marketing Strategy Creatives Campaigns Sales Agents Optimization Profits

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vladikk doit-intl.com DECOMPOSITION 02 STRATEGIES

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vladikk doit-intl.com Bounded Contexts

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vladikk doit-intl.com Domain Expert Software Developer

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vladikk doit-intl.com Business Domain Expert Software Developer ??? !!! Ubiquitous Language

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vladikk doit-intl.com Campaigns Sales Agents Your Product Marketing Strategy Creatives Optimization Profits

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vladikk doit-intl.com Sales Agent Campaign Manager ??? !!! LEAD?

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vladikk doit-intl.com Conflicting models Diﬀerent contexts Dividing the language/model Bounded Context

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vladikk doit-intl.com MarkeCng Sales Lead Lead Funnel Campaign Placement Landing Page Agency Insertion Order Message Campaign Proposition Desk Conversion Contact CDR Bounded Contexts

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vladikk doit-intl.com MarkeCng Service Sales Service DecomposiCon Strategy #1: Bounded Contexts

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vladikk doit-intl.com MarkeCng Sales Commissions Desks Sales Optimization CRM Telephony Creative Catalog Contracts Billing Campaign Management Identity & Access Ads Optimization Identity & Access

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vladikk doit-intl.com Business (Sub)Domains

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vladikk doit-intl.com Business Domain: Customer Acquisi)on Bounded Context: Marke)ng Bounded Context: Sales Subdomain: Crea)ve Catalog Subdomain: Campaigns Mngmt Subdomain: Ads Op)miza)on Subdomain: Contracts Mngmt Subdomain: CRM Subdomain: Sales Op)miza)on Subdomain: Commissions Subdomain: Desks Mngmt

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vladikk doit-intl.com DecomposiCon Strategy #2: Subomains Campaign Management Service Content Catalog Service Desks Management Service CRM Service Users Service Billing Service

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vladikk doit-intl.com Business EnCCes and Processes

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vladikk doit-intl.com MarkeCng Creative Catalog Contracts Billing Campaign Management Identity & Access Optimization Campaign Management Campaign Placement Funnel Banner Landing Page Website Zone Asset Publisher Target Market

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vladikk doit-intl.com DecomposiCon Strategy #3: EnCCes Website Asset Target Market Broker Distribu)on Customer

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vladikk doit-intl.com DecomposiCon Strategies Bounded Contexts Subdomains Business Entities and Processes

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vladikk doit-intl.com SHOW ME THE MICROSERVICES!

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vladikk doit-intl.com Bounded Contexts == Microservices ?

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vladikk doit-intl.com Sales Agent Campaign Manager ??? !!! LEAD?

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vladikk doit-intl.com MarkeCng Sales Lead Lead Funnel Campaign Placement Landing Page Agency Insertion Order Message Campaign Proposition Desk Conversion Contact CDR

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vladikk doit-intl.com MarkeCng Sales Commissions Desks Optimization CRM Telephony Creative Catalog Contracts Billing Campaign Management Identity & Access Optimization Identity & Access Lead Lead

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vladikk doit-intl.com MarkeCng Creative Catalog Campaign Management Optimization Lead Sales Commissions Optimization CRM Lead Desks Telephony Support Contracts Billing Identity & Access

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vladikk doit-intl.com Bounded Contexts Decomposi)on #1 Bounded Contexts Decomposi)on #2 Bounded Contexts Decomposi)on #3

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vladikk doit-intl.com Bounded Context Consistency boundary of the language / model Define the biggest valid monoliths Required decomposition boundary

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vladikk doit-intl.com Bounded Contexts == Microservices? No

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vladikk doit-intl.com Campaign Management Campaign Placement Funnel Banner Landing Page Website Zone Asset Publisher Target Market Campaign Website Placement Funnel MarkeCng Creative Catalog Contracts Billing Campaign Management Identity & Access Optimization Bounded Contexts? No Subdomains? EnCCes?

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vladikk doit-intl.com MICROSERVICES 03

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vladikk doit-intl.com “A service is a unit of functionality exposed to the world” - Juval Lowy “A mechanism to enable access to one or more capabilities, where the access is provided using a prescribed interface” - OASIS Service

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vladikk doit-intl.com Service Interface “Any mechanism for getting data in or out of the service” - Randy Shoup

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vladikk doit-intl.com Service Interface Asynchronous: • Producing events • Consuming events Synchronous: • Request / Response • Bulk ETL

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vladikk doit-intl.com Service Interface “Any mechanism for getting data in or out of the service” - Randy Shoup

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vladikk doit-intl.com Service Interface

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vladikk doit-intl.com Services ➜ Microservice

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vladikk doit-intl.com A microservice is a service with a micro interface

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vladikk doit-intl.com Microservice = Microinterface Reducing coupling between services Limits reasons for change Easier to understand Better fault isolation More autonomy between services

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vladikk doit-intl.com Microservice = Microinterface Reducing coupling between services Limits reasons for change Easier to understand Better fault isolation More autonomy between services

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vladikk doit-intl.com Microservice & Databases Microservices should own its database No external access Access through Microservice’s API only Database = infinite interface!

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vladikk doit-intl.com 1 Method = Perfect Microservice !!??

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vladikk doit-intl.com STAFF ONLY STAFF ONLY

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vladikk doit-intl.com The threshold upon which a system can be decomposed into microservices is defined by the use cases of the system that the microservices are a part of.

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vladikk doit-intl.com Monolith Microservices Distributed Monolith Cost of Change

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vladikk doit-intl.com Big Ball Of Mud Bounded Contexts Microservices Distributed Big Ball Of Mud Avg. Service Size

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vladikk doit-intl.com Campaign Management Campaign Placement Funnel Banner Landing Page Website Zone Asset Publisher Target Market Campaign Website Placement Funnel Subdomains? EnCCes?

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vladikk doit-intl.com ”Global complexity … the complexity of the overall structure of a program or system. I.e., the degree of association or interdependence among the major pieces of a program” Glenford J. Myers

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vladikk doit-intl.com When you design a system…, then if the features can be broken into … loosely bound groups of rela>vely closely bound features, then that division is a good thing to be made a part of the design. This is just good engineering. Tim Berners-Lee Principles of design, 1998

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vladikk doit-intl.com Services + Good Engineering = Microservices

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vladikk doit-intl.com Its is not only necessary to make sure your own system is designed to be made of modular parts. It is also necessary to realize that your own system … should always be designed to be a part of another larger system. Tim Berners-Lee Principles of design, 1998

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vladikk doit-intl.com A major part of this paper will be concerned with the ques>on of how good modularity can be achieved, that is, how modules can be chosen so as to minimize the connec5ons between them. Barbara Liskov A design methodology for reliable soIware systems, 1972

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vladikk doit-intl.com A microservice is a service with a micro interface. The threshold upon which a system can be decomposed into microservices is defined by the use cases of the system that the microservices are a part of.

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vladikk doit-intl.com A microservice is a service with a micro interface. The threshold upon which the system can be decomposed is defined by the use cases of the system that the microservices are a part of. …how to evaluate?

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vladikk doit-intl.com DESIGN 04 HEURISTICS

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vladikk doit-intl.com HeurisCc #1: Decompose to Bounded Contexts Do not implement conflicting models in the same service. Always decompose to Bounded Contexts.

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vladikk doit-intl.com HeurisCc #2: Don’t First Law of Distributed Object Design: “Don’t distribute your objects” MarCn Fowler

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vladikk doit-intl.com HeurisCc #2: Don’t Beneﬁts Addi)onal Complexity

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vladikk doit-intl.com MONOLITH SYSTEM DESIGN THAT UNDERMINES DELIVERY OF FUNCTIONAL OR NON-FUNCTIONAL REQUIREMENTS

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vladikk doit-intl.com HeurisCc #2: Don’t Beneﬁts Addi)onal Complexity

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vladikk doit-intl.com HeurisCc #2: Don’t Beneﬁts Addi)onal Complexity

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vladikk doit-intl.com Core Supporting Generic

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vladikk doit-intl.com Generic Subdomains No competitive advantage Everybody is implementing in the same way Complex business logic

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vladikk doit-intl.com MarkeCng Sales Commissions Desks Optimization CRM Telephony Creative Catalog Contracts Billing Campaign Management Identity & Access Optimization Identity & Access Generic

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vladikk doit-intl.com HeurisCc #3: Buy/Adopt Generic Subdomains Your System 3rd party product

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vladikk doit-intl.com HeurisCc #3: Buy/Adopt Generic Subdomains Your System 3rd party product An)-Corrup)on Layer

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vladikk doit-intl.com Core Subdomains Inventing something new Optimizing existing paractices Competitive advantage Complex business logic Change often

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vladikk doit-intl.com MarkeCng Sales Commissions Desks Sales Optimization CRM Telephony Creative Catalog Contracts Billing Campaign Management Identity & Access Ad Optimization Identity & Access Generic Core

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vladikk doit-intl.com Core Subdomains Inventing something new Optimizing existing paractices Competitive advantage Complex business logic Change often

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vladikk doit-intl.com HeurisCc #4: Core Subdomains - Don’t Rush Adhere to subdomain’s boundaries. Decompose further only when you acquire domain knowledge.

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vladikk doit-intl.com SupporCng Subdomains No competitive advantage Support the Core Subdomains Can’t be bought / adopted Simple business logic

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vladikk doit-intl.com SupporCng Subdomains No competitive advantage Support the Core Subdomains Can’t be bought / adopted Simple business logic

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vladikk doit-intl.com HeurisCc #5: SupporCng Subdomains - Safe Safe to decompose beyond the subdomain’s boundaries.

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vladikk doit-intl.com Core Supporting Generic

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vladikk doit-intl.com HeurisCc #6: Evaluate Consistency Requirements Method A Method B

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vladikk doit-intl.com HeurisCc #6: Evaluate Consistency Requirements Concurrency control? - Same service Method A Method B Service A

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vladikk doit-intl.com HeurisCc #6: Evaluate Consistency Requirements Read last write? - Two services, synchronous communication Service A Method A Service B Method B Sync call

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vladikk doit-intl.com HeurisCc #6: Evaluate Consistency Requirements Eventual consistency? - Two services, asynchronous communication Service A Method A Service B Method B Asynchronous Communication

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vladikk doit-intl.com HeurisCc #6: Evaluate Consistency Requirements Concurrency control? - Same service Read last write? - Two services, sync communication Eventual consistency? - Two services, async communication

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vladikk doit-intl.com Service A Method A Service B Method B Asynchronous Communication

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vladikk doit-intl.com HeurisCc #7: Public / Private Events Service Event Type 1 Event Type 2 Event Type 3 Event Type 4 Event Type 5 Event Type 6 Event Type 1000 …

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vladikk doit-intl.com HeurisCc #7: Public / Private Events Service Event Type 1 Event Type 2 Event Type 3 Event Type 4 Event Type 5 Event Type 6 Private event types (Implementation details) } Event Type 1000 …

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vladikk doit-intl.com HeurisCc #7: Public / Private Events Service Event Type 1 Event Type 2 Event Type 3 Event Type 4 Event Type 5 Event Type 6 Event Type 1000 … Private event types (Implementation details) }Public event types (Public interface) }

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vladikk doit-intl.com Service EmailChanged PhoneNumberChanged AddressChanged ContactDetailsChanged HeurisCc #7: Public / Private Events

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vladikk doit-intl.com Service EmailChanged PhoneNumberChanged AddressChanged ContactDetailsChanged Private event types (Implementation details) } Public event type (Public interface) } HeurisCc #7: Public / Private Events

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vladikk doit-intl.com HeurisCc #7: Public / Private Events Events? Domain Events State Change Events

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vladikk doit-intl.com HeurisCc #7: Public / Private Events Events? Domain Events State Change Events Private Public

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vladikk doit-intl.com HeurisCc #8: Make Events Explicit Eliminate ambiguity

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vladikk doit-intl.com HeurisCc #8: Make Events Explicit Service AgentAssignedToLead AgentAssignedToLead AgentAssignedToLead

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vladikk doit-intl.com HeurisCc #8: Make Events Explicit Service AgentAssignedToLead AgentUnassignedToLead AgentAssignedToLead

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vladikk doit-intl.com HeurisCc #9: Evaluate Reasons for Change Service A Service B

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vladikk doit-intl.com Same reasons for change? Same rate of change? Can be decoupled? Should be the same service? HeurisCc #9: Evaluate Reasons for Change

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vladikk doit-intl.com HeurisCc #10: Evaluate Services’ “Doors”

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vladikk doit-intl.com HeurisCc #10: Evaluate Services’ “Doors” STAFF ONLY STAFF ONLY

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vladikk doit-intl.com WRAP UP 05

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vladikk doit-intl.com 1. A service is a unit of func)onality exposed to the world through its public interface. 2. A microservice is a service with micro interface 3. The “micro-interface” is rela)ve to the use cases of the system that the service is a part of

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vladikk doit-intl.com Heuris)c #1: Always decompose to Bounded Contexts Heuris)c #2: Don’t go further, unless you have to Heuris)c #3: Buy/adopt generic subdomains Heuris)c #4: Core subdomains - don’t rush Heuris)c #5: Suppor)ng subdomains can be decomposed early

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vladikk doit-intl.com Heuris)c #6: Evaluate Consistency Requirements Heuris)c #7: Private / Public Events Heuris)c #8: Explicitly Deﬁne Events Heuris)c #9: Evaluate Reasons for Change Heuris)c #10: Evaluate Services’ “Doors”

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vladikk doit-intl.com Big Ball Of Mud Bounded Contexts Microservices Distributed Big Ball Of Mud Avg. Service Size

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vladikk doit-intl.com Bibliography 1. A Design Methodology for Reliable Soeware Systems, Barbara Liskov 2. Designing Autonomous Teams and Services, Nick Tune & Scoh Millet 3. Composite/Structured Design, Glenford Myers 4. Domain-Driven Design: Tackling Complexity in the Heart of Soeware, Eric Evans 5. Emerging Boundaries, Mathias Veraes 6. Implemen)ng Domain-Driven Design, Vaughn Vernon 7. Enterprise Integra)on Paherns, Gregory Hohpe, at al 8. Long Sad Story of Microservices, Greg Young 9. Managing Data in Microservices, Randy Shoup 10. Microservices, At Last Some Boundaries, Eric Evans 11. On the Criteria to be Used in Decomposing Systems Into Modules, David Parnas 12. Paherns of Enterprise Applica)on Architecture, Mar)n Fowler, at al 13. Principles of Design, Tim Berners-Lee 14. Programming WCF Services, Juval Lowy 15. What Every Programmer Should Know About Object Oriented Design, Melir Page-Jones

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https://bit.ly/2ptJ5fS THANK YOU! @vladikk vladikk.com https://bit.ly/31nSD9c http://careers.doit-intl.com

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QUESTIONS? @vladikk vladikk.com