Markelj is the founder and co-owner of Trilogic and 5logic. The main service of Trilogic is the ehrana.si service, the largest Slovenian web portal for ordering food at home, with more than 200.000 registered users and over 300 food suppliers.

5logic is developing an integrated logistics system for managing a fleet of delivery vans called AlpacaFleet.com. Markelj is experienced in programming, marketing, project management, development of web and mobile platforms.