Though I am kind of full-stack due to my long-time work experience in IT projects I specialized on IT Consulting & Agile Leadership and some fine aspects of modern IT:
SEO, UX, Frontend Engineering & Extreme Performance Optimization
And yes — vintage — I still remember the good old days fiddling with Solaris, Oracle, IBM DB2, UML & Model-driven Architecture, SED/ AWK, Perl, SH, Apache, Sendmail, ISO-8859-1, Java Applets, JBoss, Tomcat, J2EE, Grails, Groovy, Hibernate, AWT/ Spring, JQuery/ Scriptaculous, Jira/ Confluence & BIND6.
I love love love performance optimization. My rule of thumb is a Pagespeed Rank of 100% and page-loading times far beyond 80ms — no matter what network users are on.
Beyond the usual best practices of optimization and minification I love to tune the architecture to be scalable and high-available — to make users yell: Whut?!? snappy...