Queueable Apex is a way of running asynchronous Apex code that can handle complex, long-running processes. Queueable Apex can perform multiple extensive database operations and web service callouts without hitting the governor limits and system limitations. Queueable Apex can also chain the jobs to run sequentially, by implementing the Queueable interface and using the System.enqueueJob method. By using Queueable Apex, the developer can write the Apex code that can execute the processes in the background, in the order they are enqueued, and handle any errors or failures gracefully. Reference: [Queueable Apex], [Chain Jobs Using Queueable Apex]