APIs in N-tier architecture

Presented on October 11th, 2022 at Enterprise API with N-Tiered & (not only) REST architecture.

Abstract:

In this talk, we will cover the role and best practices for APIs in organizational’s multi tier architecture. We will cover the following topics:

- Introduction to mutli-tier architecture
- Layering as a architectural patterns
- Service layer pattern
- Representor pattern and hexagonal architecture
- Discovery and decoupling of components in a distributed system
- Federation, aggregation, composition and orchestration of services
- The role of API design and API governance
- Domain-driven design for APIs

Transcript

1. Zdeněk Němec, superface.ai, October '22
   APIs in N-tier architecture
   The role of APIs in modern enterprise applications
   

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2. Founder & CTO of Superface.ai
   • Pioneered the API-
   fi
   rst approach
   at Apiary.io → Oracle
   
   • Founder of API consulting Good
   API
   
   • Helped several Fortune 100
   companies with their API
   strategy and execution

   • Founder and CTO of Superface.ai
   Zdeněk “Z” Němec
   superface.ai
   

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3. APIs are connecting the world
   superface.ai
   

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4. Business
   capabilities
   Technical
   

   interfaces
   APIs
   APIs are where business capabilities meet technical interfaces
   Business + Engineering
   superface.ai
   

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5. APIs are hefty burden
   Accelerated by global pandemic, the need for API integrations grew in 80,4% of companies
   700 days
   Average time needed by a SaaS app to build API integrations
   Top SaaS apps have 7000+ integrations
   $200.000 / year
   Cost of building and running one public API
   Providing high quality APIs needs deep expertise & dedication
   > 50% dev effort
   Developers are spending more time with APIs
   49% of 28.252 Postman respondents said that more
   than half of the organization’s development e
   ff
   ort is
   spent on API
   
   superface.ai
   

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6. Challenges with APIs
   • Business and organizational alignment
   
   • API documentation
   
   • Poorly maintained API catalogs
   
   • API-design
   
   • Too many microservices
   
   • Securing API, obtaining access
   
   • Developer onboarding, hiring, and attrition
   API as deployed API as consumed
   API as documented
   NOTE: Some of these challenges are covered by Abhinav
   Asthana in https://blog.postman.com/2022-api-platform-
   landscape-trends-and-challenges
   superface.ai
   

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7. APIs in Enterprise Architecture
   Role of an architect
   Architect knows
   something about
   everything.
   
   
   Engineer knows
   everything about
   one thing.
   Understand many paradigms
   and patterns. Pick the right
   one for the task based on the
   constraints.
   superface.ai
   

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8. Follow your constraints
   Decide on architecture based on your constraints and business needs
   “I really like
   colonial houses,
   I think I’ll build
   one…”
   Houses were colonial
   because of the
   colonists were
   colonial and had
   colonial constraints
   “I really like REST
   (GraphQL) APIs,
   I think I’ll build
   one…”
   

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9. Constraints and induced properties
   API patterns: REST, GraphQL, Kafka, RPC, Flat
   fi
   le…
   Decoupled
   Evolvable
   +
   Stateless
   Reliable Scaleable
   + +
   Degraded
   ef
   fi
   ciency
   -
   Uniform

   Interface
   Simplicity
   +
   

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10. API Strategy & the role of APIs
    superface.ai
    

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11. Drivers for API
    E
    ffi
    

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12. Role of APIs
    In the API Strategy
    • APIs acknowledged and managed as a possible direct source of monetization
    (API as a product)
    API as a Product
    • APIs acknowledged and managed as an essential strategic foundation
    for creating new value chains and products (product as API)
    API as the Enterprise Applications Enabler
    superface.ai
    

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13. Layering Concept
    superface.ai
    

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14. Layering
    Breaking apart a complicated system
    • Subsystems arranged in a layer cake
    
    • Higher layer use the lower layer
    
    • …but not the layers below (encapsulation)
    
    • Lower layers are unaware of the higher
    layers
    superface.ai
    

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15. Isolation & Abstraction
    Dealing with the complexity
    • Programming language
    
    • Operating system
    
    • Device drivers
    
    • CPU instructions
    
    • Logic gates
    • HTTP
    
    • TCP
    
    • IP
    
    • Ethernet
    Programming Network communication
    superface.ai
    

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16. Benefits & Downsides
    of Layering
    • Bounded (limited) understanding
    
    • Standardization
    
    • Replacement of layers
    
    • Reusability
    
    • Minimal dependencies
    • Cascading changes
    
    • Performance impact
    
    • Complexity of the entire
    application
    
    • Time-to-delivery
    
    • Isolation of the layer’s
    responsibility
    Pros Cons
    superface.ai
    

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17. Principal layers
    superface.ai
    

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18. Three Principal Layers
    of Enterprise Application Architecture
    Presentation
    Presentation
    UI, Voice, CLI, API, …
    Domain
    Domain
    Business logic, calculation, validation, routing
    Data
    Data source
    Hidden completely from the presentation
    superface.ai
    

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19. Hexagonal architecture
    Symmetrical view
    • Similarity of the presentation and data
    source layers
    
    • Presentation & data are just connections to
    the outside world
    
    • Core surrounded by interfaces to external
    systems
    
    • Everything is an outside interface
    (symmetrical)
    https://net
    fl
    ixtechblog.com/ready-for-changes-with-
    hexagonal-architecture-b315ec967749
    superface.ai
    

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20. Architectural patterns
    Patterns of Enterprise Application Architecture
    • Domain logic patterns
    
    • Data source patterns
    
    • Object-relational patterns
    
    • Behavioral, Structural, Metadata-
    mapping, …
    
    • Web presentation patterns
    
    • MVC, Front controller, template p…
    
    • Distribution
    
    • Concurrency & session state
    superface.ai
    “An architectural pattern is a general,
    reusable solution to a commonly
    occurring problem in software
    architecture within a given context.”
    • Layered pattern
    
    • Client-server
    
    • Broker
    
    • Interpreter
    
    • Master-slave
    
    • Pipe-
    fi
    lter
    
    • Peer-to-peer
    
    • Event bus
    
    …
    

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21. Layers in a Enterprise Applications
    Cake or Cupcake?
    Monolith
    Horizontal teams
    Modular monolith, microservices
    Vertical, full-stack, end-to-end teams
    https://martinfowler.com/bliki/PresentationDomainDataLayering.html
    superface.ai
    

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22. The API Layer
    superface.ai
    

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23. API as Presentation layer
    • API is a top presentation layer
    delivering business capabilities
    
    • Drivers: direct monetization,
    added value, partner
    channels
    
    • API as a Product
    
    • API-
    fi
    rst
    
    API as a Product
    Domain
    API (Presentation)
    Data
    superface.ai
    

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24. API as interface between layers
    • Provide means of communication
    between layers
    
    • Drive revenue-generation, innovation,
    e
    ffi
    ciency
    
    • API is interface to a higher layer
    
    • Database API, Headless CMS, etc.
    API as an enabler of Enterprise Application
    Domain
    Presentation
    Data
    API
    superface.ai
    API
    

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25. Service Layer Pattern
    • Domain logic split in two sub-layers
    
    • Service / Domain model
    
    • Clear API, abstraction over domain logic
    
    • Transaction control and security
    
    • Federation
    
    • How much behavior to put in it?
    
    • API is not a domain (business) layer
    • Avoid the fallacy of ESB!
    • single point of failure
    
    • domain logic in what should have been a
    service layer
    Domain model
    Service layer (API) Domain

    layer
    Presentation
    Data
    superface.ai
    

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26. Treat every API as a public API
    presentation layer.
    superface.ai
    

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27. API Landscapes
    superface.ai
    

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28. Organizational API landscape
    Multiple enterprise applications
    superface.ai
    

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29. Multiple landscapes
    APIs landscapes are not isolated
    Stripe Azure
    Ayden
    Twilio
    Google Fedex
    …
    Global Landscape
    Global capabilities
    available within
    ACME Corp
    Partner Corp
    Service 2
    Service 1 Service 3
    Enterprise application
    CRM Inventory 2
    Orders
    Inventory 1
    PLM
    ACME Corp
    Partner Corps’
    capabilities
    superface.ai
    

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30. Presentation layer as a Data layer
    Hexagonal view
    Domain
    Frontend CLI
    API
    Data
    Order application
    Domain
    API
    Data
    Inventory service
    Data layer to the order application
    superface.ai
    

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31. Domain model
    superface.ai
    

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32. goodapi.co
    Canonical data
    model is anti-pattern
    superface.ai
    For “end-to-end” apps (modular monolith, microservices)
    

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33. Domain-driven Design
    Divide and conquer complexity by bounded context and context mapping
    Domain-driven design distilled
    • Bounded context
    Boundary within a domain
    where a particular domain
    model applies
    
    • Set of functional features
    (user stories / use cases)
    
    • A term can have di
    ff
    erent
    meaning within di
    ff
    erent
    context
    superface.ai
    

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34. API maps the Context
    Layer as a boundary
    • Layer can (but doesn’t have
    to) be a boundary
    
    • Context separation might be
    on the level of end-to-end
    modules or microservices
    superface.ai
    

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35. API
    Representor pattern
    Anticorruption layer (ACL)
    • Mapping between your domain and
    other bounded context / 3rd party
    dependencies
    
    • Shield your layer from cascading
    changes
    
    • Integrate heterogenous systems within
    an enterprise
    
    • ESB served this purpose
    Domain API
    representor (adapter)
    superface.ai
    

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36. REST
    Representational state transfer
    • Manipulation of resources through their representations
    • REST API server exposes representation of resources over a message format
    (content-type)
    
    • Client then uses representor pattern to map API’s representation to its own
    domain model
    superface.ai
    Domain Domain
    API Data
    representor
    representor
    representations
    

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37. Key takeaways
    • Layering to manage complexity, promote reusability, minimize dependencies
    
    • Three fundamental layers: presentation, domain, data
    
    • Hexagonal architecture is a symmetrical view of principal layers
    
    • Split large layers vertically with modular monolith or microservies
    
    • API is a presentation (service) layer, avoid domain logic in it
    
    • Presentation layer might be a data layer to another app
    
    • Divide domain model into context, map context in APIs with representor pattern
    superface.ai
    

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38. Questions?
    superface.ai
    5 books for
    fi
    rst 5 questions
    

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39. Thank you!
    Let’s talk!
    Superface.ai – the open source
    framework for Autonomous APIs
    https://github.com/superfaceai
    Zdenek “Z” Nemec 

    Twitter: @zdne
    
    superface.ai
    superface.ai
    

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