Architectures for reconfigurable and self-adaptive systems -- Dynamic Updates of Virtual PLCs deployed as Kubernetes Microservices -- A runtime safety enforcement approach by monitoring and adaptation -- Towards a Taxonomy of Autonomous Systems -- Machine learning for Software Architecture -- Explaining Architectural Tradeoff Spaces: a Machine Learning Approach -- A Machine Learning Approach to Service Discovery for Microservice Architectures -- FLRA: A Reference Architecture for Federated Learning Systems -- Architectural knowledge, decisions, and rationale -- Tracelink Recovery for Software Architecture Documentation -- An Exploratory Study on Architectural Knowledge in Issue Tracking Systems -- Human Behavior-Oriented Architectural Design -- Architecting for Quality Attributes -- Updating Service-based Software Systems in Air-Gapped Environments -- Energy-Aware Robotics Software: A Catalog of Architectural Tactics from the ROS Ecosystem -- Taxonomy of Edge Blockchain Network Designs -- Impact analysis of software parallelism in big data technologies for data-intensive architectures -- Architecture-centric Source Code Analysis -- State of the Practice in Application Programming Interfaces (APIs): A Case Study -- Identifying Domain-Based Cyclic Dependencies in Microservice APIs Using Source Code Detectors -- Optimized Dependency Weights in Source Code Clustering -- Experiences and Learnings from Industrial Case Studies -- Reliable Event Routing in the Cloud and on the Edge: An Internet-of-Things Solution in the AgeTech Domain -- An Experience Report on Modernizing I/O Configuration Software -- Enabling SMEs to Industry 4.0 using the BaSyx middleware: a case study -- Software Architectures for Edge Analytics: A Survey -- How Software Architects Focus Their Attention.

This book constitutes the refereed proceedings of the 15th International Conference on Software Architecture, ECSA 2021, held in Sweden, in September 2021. Due to the COVID-19 pandemic, the conference was held virtually. For the Research Track, 11 full papers, presented together with 5 short papers, were carefully reviewed and selected from 58 submissions. The papers are organized in topical sections as follows: architectures for reconfigurable and self-adaptive systems; machine learning for software architecture; architectural knowledge, decisions, and rationale; architecting for quality attributes; architecture-centric source code analysis; and experiences and learnings from industrial case studies.