The paper describing the details of AiiDA’s workflow engine has been published today:
M. Uhrin et al, Workflows in AiiDA: Engineering a high-throughput, event-based engine for robust and modular computational workflows, Comp. Mat. Sci. 187, 110086 (2021)
In it you will find useful details on how the AiiDA process engine (managing calculation and workflows) works in the AiiDA 1.x series, bringing a huge speed-up with respect to earlier versions also thanks to the event-based design, leveraging the RabbitMQ message broker.
We would be grateful it users running simulations with AiiDA 1.x could cite it along with the main reference paper S.P. Huber et al., Scientific Data 7, 300 (2020).