Building an Order Processing Saga with MassTransit

Leader posted 1 min read

MassTransit has been around since 2007 and has matured into one of the most stable and feature-rich open-source .NET messaging frameworks.

It acts like a factory for message brokers, meaning you can switch between providers such as RabbitMQ, Azure Service Bus, ActiveMQ, Amazon SQS, and others with minimal configuration changes.

This makes it ideal for enterprise-grade distributed systems where you want flexibility without vendor lock-in.

Why MassTransit?

Stability: Over a decade of continuous development and production use.

Multi-Broker Support: Easily swap between Azure Service Bus, RabbitMQ, Amazon SQS, etc., without rewriting business logic.

Developer Friendly: Built for .NET developers with excellent documentation and integration with DI, EF Core, and ASP.NET Core.

Advanced Features:

  • Outbox pattern

  • Request/Response messaging

  • Retry and circuit-breaker policies

  • Sagas and State Machines

  • Message scheduling

One of the Coolest Features: The State Machine

A State Machine allows you to model complex workflows where messages arrive in any order, but your application processes them in a controlled, state-aware sequence.

For example, in this Order Processing Saga:

  • An order is submitted.

  • The saga waits for stock confirmation.

  • If stock is reserved, the saga waits for payment authorization.

  • Once payment is authorized, the order is marked as completed.

  • If any step fails, the saga can transition to a failed state and trigger compensating actions.

This approach eliminates spaghetti code for multi-step processes and makes workflows easy to visualize and maintain.

Technology Stack Used in This Project
.NET 9

  • MassTransit (with Saga State Machine)

  • RabbitMQ (message broker)

  • PostgreSQL (saga persistence)

  • Entity Framework Core (database access)

  • Docker (local RabbitMQ/PostgreSQL setup)

Source Code
Full working implementation available here:
GitHub – OutboxSagaDemo

References

MassTransit Documentation – https://masstransit.io/

MassTransit GitHub Repository – https://github.com/MassTransit/MassTransit

MassTransit Saga State Machine Guide – https://masstransit.io/documentation/patterns/saga

RabbitMQ Documentation – https://www.rabbitmq.com/documentation.html

PostgreSQL Documentation – https://www.postgresql.org/docs/

Entity Framework Core Docs – https://learn.microsoft.com/en-us/ef/core/

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