Building a Robust Reservation System with Event-Driven Architecture

Building a Robust Reservation System with Event-Driven Architecture In this post, I’ll guide you through creating a scalable reservation system using event-driven architecture. We’ll explore domain modeling, event handling, and message processing - essential concepts for modern distributed systems. The Reservation Process Flow Let’s start by visualizing the reservation workflow with a Mermaid diagram: flowchart TD A[Start Reservation Process] --> B[Receive Reservation Request] B --> C{Validate Request} C -->|Valid| D[Check Availability] C -->|Invalid| E[Return Error to Client] D --> F{Availability?} F -->|Available| G[Create Reservation] F -->|Not Available| H[Notify Client of Unavailability] G --> I[Send Confirmation via Wolverine] H --> I I --> J[Store Reservation in Postgres] J --> K[Return Success Response to Client] E --> L[End Process] K --> L This diagram shows the end-to-end process from receiving a request to returning a response, with key decision points and actions along the way. ...

April 2, 2025 · 5 min · Taner

Building a Robust Reservation System: A Step-by-Step Guide

1. Define Your Requirements Before diving into code, clarify the system’s core functionalities. For a reservation system, we might consider: Booking Management: Creating, updating, and canceling reservations. Availability Checking: Ensuring that double-booking or conflicts are prevented. Customer Management: Handling user details, authentication, and notifications. Resource or Venue Management: Tracking the items or spaces being reserved. Concurrency Control: Managing simultaneous booking attempts (e.g., using transactions and locks). Understanding these requirements will help guide your design decisions. ...

April 2, 2025 · 5 min · Taner

Designing Event-Based Systems with Wolverine: A Comprehensive Guide

Designing an event-based system with Wolverine is an exciting challenge that leverages asynchronous messaging to decouple components and build a resilient architecture. Here’s a comprehensive pathway to help you get started: 1. Understand the Role of Wolverine Wolverine is a lightweight, .NET-native messaging framework designed to help you craft robust, event-driven applications. It facilitates: Message Routing: Seamlessly route events and commands to corresponding handlers. Transport Flexibility: Integrate with in-memory queues or external messaging systems such as RabbitMQ or Azure Service Bus. Resilience and Durability: Apply advanced patterns like retry, scheduling, and outbox support if needed. By using Wolverine, you can focus on business logic while the framework handles much of the messaging infrastructure. ...

April 2, 2025 · 4 min · Taner

Understanding CQRS: Command Query Responsibility Segregation

Understanding CQRS: Command Query Responsibility Segregation Command Query Responsibility Segregation (CQRS) is an architectural pattern that separates read and write operations into distinct models. This separation allows for optimization of each model independently, addressing different requirements and scaling needs. Core Components of CQRS flowchart TD Client[Client Application] --> Commands[Commands] Client --> Queries[Queries] Commands --> CommandHandler[Command Handler] Queries --> QueryHandler[Query Handler] CommandHandler --> WriteModel[Write Model/Domain Model] WriteModel --> EventStore[Event Store] EventStore --> ReadModelProjection[Read Model Projection] ReadModelProjection --> ReadModel[Read Model] QueryHandler --> ReadModel ReadModel --> QueryResults[Query Results] QueryResults --> Client Key Components and Their Responsibilities: Commands: Instructions to change state (e.g., CreateOrder, UpdateCustomer). Queries: Requests for information without state changes. Command Handler: Processes commands and applies them to the write model. Write Model: The domain model with rich business logic. Event Store: Records all state-changing events as the source of truth. Read Model Projection: Processes events to update the read model. Read Model: Optimized for querying, often denormalized for performance. Query Handler: Retrieves data from the Read Model in response to queries. The separation of write and read models allows for independent optimization, scalability, and security for both operations. ...

March 28, 2025 · 2 min · Taner

Exploring Major Software Architecture Patterns: A Comprehensive Guide

Exploring Major Software Architecture Patterns: A Comprehensive Guide Here are 20 major software architecture patterns along with brief explanations: Layered (N-Tier) Architecture: Organizes software into layers, each with a specific responsibility, such as presentation, business logic, and data access. This separation enhances maintainability and scalability. Microservices Architecture: Breaks down an application into small, independent services that communicate over a network. This allows for flexible scaling and deployment. Event-Driven Architecture (EDA): Uses events to trigger and communicate between decoupled services. It is highly scalable and suitable for real-time processing. ...

March 27, 2025 · 3 min · Taner

Mastering System Design: The Importance of Clear Diagrams

Mastering System Design Through Diagrams: A Personal Journey A few years ago, I found myself in an interview where I was asked about architecture diagrams—and honestly, I choked. That moment was a wake-up call. I realized that if I wanted to be confident in system design and convey my ideas clearly, I needed to make diagrams a core part of my process. Today, I’m sharing my step-by-step approach to diagramming through the various stages of system development. Not only will this guide help you in interviews, but it also serves as a roadmap to developing well-thought-out systems. ...

March 27, 2025 · 5 min · Taner

High-Level Context Diagram for Event-Based Reservation Systems Using Wolverine

Below is an example of a Mermaid diagram that shows a high-level context diagram for our event-based reservation system using Wolverine. In this diagram, you can see external actors (like customers, an administrator, payment gateway, etc.) interacting with internal components such as a Reservation Frontend, Reservation Service, and the Wolverine Event Bus responsible for handling events. flowchart LR %%External Actors Customer[Customer] PaymentGateway[Payment Gateway] NotificationService[Notification Service] Administrator[Administrator] ResourceCatalog[Resource Catalog] %%Internal System Components subgraph System [Reservation System] Frontend[Reservation Frontend] Service[Reservation Service] EventBus[Wolverine Event Bus] end %%Interactions between External Actors and the System Customer -->|Creates/Manages Booking| Frontend Frontend --> Service Service -->|Publishes Events| EventBus EventBus -->|Notifies| PaymentGateway EventBus -->|Notifies| NotificationService Service -->|Checks Availability| ResourceCatalog Administrator -->|Manages System| Service Explanation External Actors: ...

April 2, 2025 · 2 min · Taner

Use Case Diagram for Event-Based Reservation Systems

Here is a Use Case Diagram for our reservation system, which visualizes the interactions between users (actors) and the system’s functionalities (use cases). graph TD %% External Actors Customer[Customer] --> CreateReservation Customer --> CancelReservation Customer --> ViewReservationDetails Customer --> ReceiveNotifications Administrator[Administrator] --> ManageResources Administrator --> GenerateReports Administrator --> ViewCustomerDetails %% System subgraph ReservationSystem [Reservation System] CreateReservation[Create Reservation] CancelReservation[Cancel Reservation] ViewReservationDetails[View Reservation Details] ReceiveNotifications[Receive Notifications] ManageResources[Manage Resources] GenerateReports[Generate Reports] ViewCustomerDetails[View Customer Details] end Explanation of the Diagram Actors: ...

April 2, 2025 · 1 min · Taner

Component Design for Event-Based Reservation Systems: Wolverine Integration

Below is a Mermaid diagram that outlines a component diagram for your event-based reservation system using Wolverine. This diagram breaks down the core components and shows how they interact with each other and with external systems. graph TD %% External Systems PG[Payment Gateway] NS[Notification Service] RC[Resource Catalog] %% Reservation System Components subgraph Reservation_System [Reservation System] FE[Reservation Frontend] RS[Reservation Service] DO[Durable Outbox] EB[Wolverine Event Bus] EH[Event Handlers] end %% Internal Interactions FE -->|User Requests| RS RS -->|Persists Events/Commands| DO RS -->|Publishes Events| EB EB --> EH RS -->|Checks Availability| RC %% External Interactions via Event Bus EB -->|Notifies| PG EB -->|Notifies| NS Explanation Reservation System Components: ...

April 2, 2025 · 2 min · Taner

Level-1 Data Flow Diagram for Event-Based Reservation Systems

Here’s an example of a Level-1 Data Flow Diagram (DFD) for our reservation system. It highlights how data moves between external entities, processes, and storage components. flowchart TD %% External Entities Customer[Customer] ResourceCatalog[Resource Catalog] PaymentGateway[Payment Gateway] NotificationService[Notification Service] %% Processes Process1[Submit Reservation] Process2[Check Resource Availability] Process3[Process Payment] Process4[Notify Customer] %% Data Stores D1[Reservation Data Store] D2[Customer Data Store] %% Data Flows Customer -->|Reservation Details| Process1 Process1 -->|Reservation Data| D1 Process1 -->|Customer Details| D2 Process1 -->|Resource Details| Process2 ResourceCatalog -->|Resource Availability| Process2 Process2 -->|Reservation Confirmation| Process1 Process1 -->|Payment Info| Process3 PaymentGateway -->|Payment Status| Process3 Process3 -->|Notification Request| Process4 Process4 -->|Notification| NotificationService Explanation External Entities: ...

April 2, 2025 · 2 min · Taner

Exploring Class Design for Event-Driven Reservation Systems: Mermaid Diagram Representation

Below is an example of a Mermaid class diagram representing the core classes for our event-based reservation system to visualize the relationships between the entities, services, and events. classDiagram %% Domain Entities class Customer { +int Id +string FullName +string Email } class Resource { +int Id +string Name +string Description } class Reservation { +int Id +int CustomerId +int ResourceId +DateTime StartDate +DateTime EndDate +ReservationStatus Status } %% Service Layer class ReservationService { +CreateReservation(customerId: int, resourceId: int, startDate: DateTime, endDate: DateTime) Reservation +CancelReservation(reservationId: int) bool } %% Domain Events class ReservationCreatedEvent { +Guid ReservationId +DateTime CreatedAt +int CustomerId } class ReservationCancelledEvent { +Guid ReservationId +DateTime CancelledAt +int CustomerId } %% Event Handling Component class ReservationEventHandler { +Handle(event: ReservationCreatedEvent) +Handle(event: ReservationCancelledEvent) } %% Associations Customer "1" --o "0..*" Reservation : creates Resource "1" --o "0..*" Reservation : assigned to ReservationService ..> ReservationCreatedEvent : publishes ReservationService ..> ReservationCancelledEvent : publishes ReservationEventHandler ..> ReservationCreatedEvent : handles ReservationEventHandler ..> ReservationCancelledEvent : handles %% Note: ReservationStatus is an enumeration (e.g., Pending, Confirmed, Cancelled) Explanation Domain Entities: ...

April 2, 2025 · 2 min · Taner

Sequence Diagram for Event-Based Reservation Workflow Using Wolverine

Below is a Mermaid sequence diagram that showcases how components of our event-based reservation system interact during a typical workflow. This example outlines the process of a customer creating a reservation and includes key components such as the frontend, service layer, Wolverine event bus, and external systems. sequenceDiagram participant Customer participant Frontend participant Service as Reservation Service participant EventBus as Wolverine Event Bus participant ResourceCatalog participant Notification as Notification Service Customer ->> Frontend: Request to create a reservation Frontend ->> Service: Submit reservation details Service ->> ResourceCatalog: Check resource availability ResourceCatalog -->> Service: Availability status Service ->> Service: Validate and process reservation Service ->> EventBus: Publish ReservationCreated event EventBus ->> Notification: Notify customer of confirmation EventBus -->> Service: Acknowledge event publishing Service -->> Frontend: Return confirmation to customer Frontend -->> Customer: Display confirmation details Explanation of the Workflow Customer Interaction: ...

April 2, 2025 · 2 min · Taner

System Sequence Diagram for Reservation Workflow

Below is a System Sequence Diagram for a reservation system, which highlights the interaction between external actors (e.g., customer, administrator) and the system during a reservation workflow: sequenceDiagram participant Customer participant System as Reservation System Customer ->> System: Enter reservation details System -->> Customer: Validate inputs Customer ->> System: Submit reservation request System ->> System: Check resource availability alt Resource available System ->> System: Create reservation System ->> Customer: Confirm reservation System ->> System: Trigger payment process System ->> Customer: Notify payment status else Resource not available System ->> Customer: Display unavailability message end Explanation of the Diagram: Actors and System: ...

April 2, 2025 · 1 min · Taner

State Diagram for Reservation Lifecycle in Event-Based Systems

Here’s an example of a State Diagram for a reservation system object. This illustrates the states that a reservation can move through and the transitions triggered by events or actions. stateDiagram-v2 state "Pending" as Pending state "Confirmed" as Confirmed state "Cancelled" as Cancelled state "Completed" as Completed %% State Transitions Pending --> Confirmed: Payment Received Pending --> Cancelled: Customer Cancels Confirmed --> Cancelled: Customer Cancels Confirmed --> Completed: Reservation Period Ends Cancelled --> Pending: Reopen Request Explanation of States and Transitions: States: ...

April 2, 2025 · 1 min · Taner

Creating a Seamless Reservation Workflow with Mermaid Diagrams in Hugo

Visualizing Reservation Workflows with Mermaid in Hugo Mermaid diagrams offer a fantastic way to visualize workflows, decisions, and parallel processes in a clear, easy-to-understand format. Below, you’ll find a Mermaid activity diagram that highlights the workflow of creating a reservation in your system. This workflow includes decision points (e.g., checking resource availability) and parallel processes (e.g., notifying external systems like payment gateways or customer notification services). You can copy and paste the code into a Mermaid-enabled editor to visualize the diagram. ...

April 1, 2025 · 2 min · Taner

Deployment Diagram for Event-Based Reservation Systems Using Wolverine

Below is an example of a deployment diagram for our event-based reservation system. This shows how components of the system are deployed across servers, environments, and external services in a physical setup. You can use the following Mermaid code to visualize it in a Mermaid-enabled renderer: graph TD %% Deployment Nodes subgraph ClientMachine [Client Machine] FrontendApp[Reservation Frontend App] end subgraph AppServer [Application Server] ReservationService[Reservation Service] WolverineEventBus[Wolverine Event Bus] DurableOutbox[Durable Outbox] end subgraph Messaging [Messaging Infrastructure] MessageBroker[Message Broker] end subgraph DatabaseServer [Database Server] ReservationsDB[Reservations Database] CustomersDB[Customers Database] end subgraph ExternalServices [External Systems] PaymentGateway[Payment Gateway] NotificationService[Notification Service] ResourceCatalog[Resource Catalog Service] end %% Interactions FrontendApp --> ReservationService ReservationService --> WolverineEventBus WolverineEventBus --> DurableOutbox WolverineEventBus --> MessageBroker MessageBroker --> PaymentGateway MessageBroker --> NotificationService ReservationService --> ReservationsDB ReservationService --> CustomersDB ReservationService --> ResourceCatalog Explanation Nodes: ...

April 2, 2025 · 2 min · Taner

Entity-Relationship Diagram for Event-Based Reservation Systems

Here is a conceptual Entity-Relationship Diagram (ERD) for our conceptual reservation system. This diagram includes entities such as Customer, Reservation, and Resource, along with their attributes and relationships. erDiagram %% Customer Entity Customer { int Id string FullName string Email string Phone } %% Resource Entity Resource { int Id string Name string Description int Capacity } %% Reservation Entity Reservation { int Id int CustomerId int ResourceId DateTime StartDate DateTime EndDate string Status } %% Relationships Customer ||--o{ Reservation : "creates" Resource ||--o{ Reservation : "associated with" Explanation Entities: ...

April 2, 2025 · 1 min · Taner

Network Diagram for Securing Event-Based Reservation Systems

Below is an example of a Network Diagram that depicts a possible topology for our reservation system, illustrating firewalls, routers, subnets, and connections. It is designed to enhance network security and efficiency. graph TB %% Internet Internet[Internet] --> Firewall1[Firewall] %% Perimeter Network -DMZ subgraph DMZ[Perimeter Network -DMZ-] Router[Router] APIGateway[API Gateway] end Firewall1 --> Router Router --> APIGateway %% Internal Network subgraph InternalNetwork[Internal Network] LoadBalancer[Load Balancer] ApplicationServer1[App Server 1] ApplicationServer2[App Server 2] DatabaseServer[Database Server] EventBus[Wolverine Event Bus] end APIGateway --> LoadBalancer LoadBalancer --> ApplicationServer1 LoadBalancer --> ApplicationServer2 ApplicationServer1 --> DatabaseServer ApplicationServer2 --> DatabaseServer ApplicationServer1 --> EventBus ApplicationServer2 --> EventBus %% External Services subgraph ExternalServices[External Services] NotificationService[Notification Service] PaymentGateway[Payment Gateway] end EventBus --> NotificationService EventBus --> PaymentGateway Components Breakdown: Internet: ...

April 2, 2025 · 2 min · Taner