nightly.link is a web application that provides shareable links to download the latest build artifacts from GitHub Actions workflows. It acts as a proxy that uses a GitHub App to obtain installation tokens for accessing repository artifacts, bypassing the requirement for users to be logged into GitHub. The application is built with Crystal and features a modular architecture with separate components for routing, GitHub API interaction, caching, and utilities. Key routes handle URL parsing, workflow run lookup, artifact retrieval, and redirect to temporary download URLs. The system caches installation tokens and API responses to minimize GitHub API calls and uses a SQLite database to persist installation data for user-authorized repositories.