Technologies for managed code execution include a computing device having a processor with protection key support. The computing device sets a protection key register of the processor with permissions to disallow data access to any protection domain of the computing device and then executes a domain switch routine to switch to a managed applet. The managed applet is included in an applet protection domain, the domain switch routine is included in a switch protection domain, and a managed runtime environment is included in a normal protection domain. The domain switch routine sets the protection key register with permissions to disallow access to any protection domain other than the applet protection domain and then executes the managed applet. Other managed applets may be each be included in separate applet domains. Each managed applet may be a thread executed within a common process address space. Other embodiments are described and claimed.