Party Reservation

An application to make party reservations.

Design

The Use Case

I want to make a party reservation through the Reservation Entry service, and have that reservation asynchronously propagated to the Reservation Confirmation service. This ensures that when the doorman checks the guest list on their device, my RSVP appears without requiring direct communication between the two services. The interaction should be seamless, event-driven, and decoupled. Each service operates independently while exchanging information through events.

The Problem

Traditional microservice communication often relies on synchronous HTTP calls, which introduce tight coupling between services. In such setups, consumer services must understand the producer’s domain and API contracts, making them fragile and harder to scale. As the number of producers grows, this dependency web becomes increasingly complex, limiting flexibility and introducing integration overhead. Achieving true autonomy and resilience in microservices requires eliminating these direct dependencies.

The Goal

The objective is to decouple microservices by adopting a messaging-driven architecture using Kafka as the event backbone. Instead of REST-based communication, services publish and consume events asynchronously. The Reservation Entry service acts as a publisher, emitting reservation events to Kafka without any knowledge of who consumes them. The Reservation Confirmation service acts as a subscriber, reacting to these events and updating the client in real time via Server-Sent Events (SSE). This approach ensures:

• Loose coupling: Producers and consumers remain independent.
• Technology agnosticism: Consumers can use any stack or language.
• Scalability and resilience: New consumers can subscribe without impacting existing producers.

Swagger

Reservation Confirmation Service

http://localhost:8081/webjars/swagger-ui/index.html?configUrl=/v3/api-docs/swagger-config

Docker

• To start both microservices in docker you need to run: docker-compose up or docker-compose up -d without the daemon attached to your console.
• This will start the confirmation service on localhost:8081 and the reservation service on localhost:8080
• To stop the services from running while the daemon is attached to your console you need to run ctrl + c.