Web3 ProviderEngine

Web3 ProviderEngine is a JavaScript library designed for composing custom Ethereum provider objects using a stack of middleware-like modules called 'sub-providers'. It enables fine-grained control over RPC requests, facilitating features like caching and custom transaction signing workflows. Originally developed for MetaMask, this package has been officially deprecated since version 17.0.0, released in March 2023. Development has largely ceased, and the current stable version is 17.0.1. Users are strongly advised to migrate to modern alternatives such as `@metamask/json-rpc-engine`, `@metamask/eth-json-rpc-middleware`, and `@metamask/eth-json-rpc-provider`. Its key differentiator was its highly modular architecture, allowing developers to assemble a customized provider pipeline for diverse DApp requirements, acting as a 'zero-client' that processes local requests and passes data lookups to a data source.