The 27th edition of the International Conference on Real-Time Networks and Systems (RTNS) was held November 6–8, 2019, in Toulouse, France. RTNS is a friendly conference with a great sense of community that offers excellent opportunities for collaboration as well as a high-quality technical program. RTNS publishes papers addressing real-time issues in any area of computation and communication, at any level of abstraction, and in any application domain. The reviewing process involved 44 program committee members, who were assisted by 22 additional reviewers, and each submission received at least three reviews. Of 37 submissions that were received, 20 papers were accepted for publication at RTNS 2019. From the 20 accepted papers, 4 were chosen as outstanding papers, and the authors of those papers were invited to submit extended articles for this special issue, containing significant additional technical content beyond the contributions that were published at RTNS 2019. Each of those articles underwent a rigorous additional review process, involving new reviewers who had not originally reviewed the papers, as well as reviewers who had evaluated them for RTNS 2019, and with each article receiving three reviews in this stage as well. Following multiple rounds of reviewing and revision, leading ultimately to approval, each of the four articles that appears in this special issue provides new technical advances in the state of the art for real-time networks and systems.