Cloud-based communications technologies provide a primary layer for today's real-time (synchronous), computerized (on-line) second language learning because of their ability to offer low-latency interactions, mutable modes of support (multimodal) and analytics-based instructional support. This research study can be deemed an extended IMRAD study of how elements associated with the quality-of-service (QoS) (latency, jitter, packet loss) of the underlying supporting infrastructure and methods of delivering that infrastructure (such as edge computing, autoscaling) and techniques for preserving student privacy through analytics can have an impact on the instructional design (task-based learning, timely feedback, role-structured communication) used to achieve desired instructional outcomes and benefits of SCMC (synchronous computer-mediated communication). Based on a quasi-experimental mixed-methods design using pre-/post-testing, learning analytics, and discourse analysis (N = 124), this study estimates the unique impact of stability in the infrastructure on learners' gains in speaking fluency, interactional competence, pronunciation accuracy and learner engagement during a 10-week period of learning. Findings from the study indicate that optimizing the supporting infrastructure has moderate effect sizes on fluency and interactional competence, as well as interactions between pedagogies and infrastructures. This research study provides design guidelines for resilient deployment of CBCT as aligned with the principles of communicative language teaching.