KurrentDB

Booking Microservices is a practical flight-booking system developed by Evangelos Vlachos as a set of .NET 10 microservices. It uses Vertical Slice Architecture, domain-driven design, CQRS, and event sourcing; commands update PostgreSQL or EventStoreDB and publish integration events through Wolverine's durable outbox to RabbitMQ, while consumers use a durable inbox to project read models into MongoDB. Queries read from MongoDB, and synchronous cross-service validation uses gRPC. The repository includes Identity, Flight, Passenger, Booking, and YARP API gateway services, plus .NET Aspire orchestration, Docker Compose and Kubernetes deployment configurations, OpenTelemetry-based observability, OpenAPI documentation, and automated unit, integration, end-to-end, and contract tests.

Apache Kafka is an open-source distributed event-streaming platform developed by the Apache Software Foundation. It is used for high-performance data pipelines, streaming analytics, data integration, and mission-critical applications, and can be deployed on premises, in a cluster, or through a managed service. The official repository contains Java and Scala source code, build tasks, documentation generation, and unit and integration tests.

Confluent is an event-streaming platform used in the described system to carry live event messages from a win-probability system to downstream processing. That processing determines whether an event is a key moment and generates explanatory text.

Sockudo is a self-hosted, high-performance Rust real-time server for WebSocket and HTTP publishing. It targets strict Pusher Protocol V1 compatibility for drop-in use, while Protocol V2 adds Sockudo-native events, serials, message IDs, recovery, rewind, tags, deltas, annotations, and mutable message events. The platform supports durable history, hot replay buffers, two-tier recovery, presence history, push notifications, webhooks, rate limiting, TLS, Prometheus metrics, Docker Compose, and Helm. Horizontal fanout can use Redis, Redis Cluster, NATS, RabbitMQ, Google Pub/Sub, Kafka, Pulsar, or Apache Iggy. The monorepo includes the Rust server and workspace crates, dashboards, deployment assets, documentation, official real-time and server SDKs, and an optional AI Transport SDK.

MongoDB is a document database and data platform used in the booking backend's CQRS data architecture. Its document data model is designed to map to application access patterns, and its query API supports lookups, processing pipelines, analytics, and data transformations. MongoDB Atlas combines operational data, vector search, streaming, text search, analytical, graph, and geospatial capabilities in a unified platform.