Devices having one or more of the following: an input/output (I/O) interconnect system, an optical I/O interconnect, an electrical I/O interconnect, a radio frequency I/O interconnect, are disclosed. A representative I/O interconnect system includes a first substrate and a second substrate. The first substrate includes a compliant pillar vertically extending from the first substrate. The compliant pillar is constructed of a first material. The second substrate includes a compliant socket adapted to receive the compliant pillar. The compliant socket is constructed of a second material.