Asynchronous processing in Java historically considered complex and error-prone, with multiple approaches to tackle the issue.Promises with a functional style API offer straightforward code, minimal technical details leakage, and a simple mental model.Push and pull processing models dictate how pipelines receive messages for processing, with push model being event-driven.Promise<T> represents an asynchronous computation that can succeed or fail, with main states of pending and resolved.Promise<T> has transformation methods like map() and flatMap(), and side effect methods like onResult() for async operations.Functional style Promises API includes creating promises, transforming other monads into promises, and launching async operations.Patterns like Sequencer (sequential execution) and Fork-Join (parallel execution) efficiently implemented with Promise<T>.Typical asynchronous processing patterns include Sequencer, Fork-Join (like all(), any(), allOf() predicates), error recovery, retrying, and circuit breaker.Pragmatica Lite Core Library offers implementations of core monads and utility classes for handling promises and asynchronous processing.Functional style Promise<T> simplifies asynchronous coding, with a focus on clarity, scalability, and easy reasoning about complex business logic.