All transactions processed by the LMAX system are ACID. The application is modelled such that each input event represents one transaction. Where business transaction span multiple nodes, rather than handle the complexity of retaining ACID properties across multiple messages, our reliable messaging system ensures delivery to a remote system and queuing a message is included in the same transaction context as the business logic. This is true of services that use a high speed journal (event-sourced) and those that perform more traditional database operations. Long running transactions become steps in a state model.