C++, Perl, multithreading, Internet standards and protocols, API design, high-throughput networking, SQL, web design, multiplatform design
I cofounded this e-mail technology startup.
Zanshin went through three incarnations. First we created a desktop e-mail client (in multithreaded, cross-platform C++) with power-user features that was fast and beautiful. But while we were writing it, Microsoft and Netscape gave away adequate mail clients for free, destroying the market and our ability to capitalize on our creation.
Next we built an ambitious e-mail server, also in C++, with a piecewise relational schema for storing e-mail, the ability to construct dynamic views on different "slices" of your personal e-mail space on the fly, and a facility for annotating inbound and outbound messages with web-based functionality. Our marketing efforts on this powerful but difficult-to-describe technology fell flat.
Finally we implemented a delivery and reporting service for opt-in marketing e-mail (not spam!), which found considerable success. I created the specialized, ultra-high-performance e-mail delivery engine, able to customize each message for each recipient on the fly, still in use today. Nearly all of this was written in Perl.