This course presents the basic concepts and solution principles of distributed systems. The main topics are synchronization, consistency, fault tolerance, distributed consensus, and security. The course considers different kinds of distributed systems, from modern warehouse-scale datacenters to wide-area, loosely-coupled distributed systems. The focus is on gaining an understanding on how modern distributed systems are designed and built and what are their theoretical underpinnings. The course covers the basic algorithms of distributed systems and the current state of research in the area. Course material: Largely based on research articles and supplemental material. Selected material from the book "Barroso, L. A., Clidaras, J. and Hölzle, U.: The Datacenter as a Computer¿. (book is available online)