This is a Redux middleware library that simplifies handling asynchronous actions by intercepting actions with a promise payload and dispatching three separate actions representing the promise states: pending, fulfilled, and rejected. It supports implicit and explicit promise definitions, async functions, optimistic updates via payload.data, and custom type suffixes and delimiters. The middleware is well-structured, fully tested with a comprehensive suite covering edge cases like null/boolean/numeric resolutions, async functions, and third-party promise libraries. It is a mature, stable library with nearly 2000 stars, widely used in the Redux ecosystem. The codebase is clean and follows best practices, though it uses some older tooling versions (Babel 7, Jest 24, Webpack 4).