Front end (jQuery/JS/ES6/JSX, SASS/CSS, HTML, Gulp, NPM, semantic, UX design, UI design, typography, hundreds of libraries) Back end (C#, .NET, PHP, Node.js, Swift, Java, a few others) Database (MySQL, SQL Server, PostgreSQL, MongoDB, Oracle, MariaDB, data modeling) Specification (RESTful, CSS BEM, code design pattern, security) Methodology (Mobile first, responsive, agile) Web server (Linux, Windows) Version Control (Git) Cloud computing (Amazon AWS, Digital Ocean) Caching (CDN, .NET Core, a few others) Virtualization (Docker) Cryptocurrency