5G New Radio (NR) is envisioned to support three broad categories of services: evolved mobile broadband (eMBB), ultra-reliable and low-latency communications (URLLC), and massive machine-type communications (mMTC). The URLLC services refer to future applications that require secure data communications from one end to another with ultra-high reliability and deadline-based low latency requirements. This type of quality-of-service is vastly different from that of traditional mobile broadband applications. In this paper, we discuss the systems design principles to enable the URLLC services in 5G. Theoretical queueing analysis and system-level simulations are provided to support these systems design choices, many of which have been considered as work items in the 3GPP Release 15 standards, which will be the first release for 5G NR.