Databases technology and setup based on application needs, e.g. SQL (cluster), TDSB and noSQL databases.
Open source solution setup, configuration and customization based on client needs for: automation, communication (email, IM, XMPP, SIP), CMS, DNS, gateway, proxy, IoT, streaming, monitoring, file-sharing, collaboration, dashboards, task/project manager, vpn, web server, wikis, continuous integration...