This report documents program and outcomes of Dagstuhl Seminar 21071 Data Structure. Even if field of data structures is quite mature, new trends and limitations in computer hardware together with ever-increasing amounts of data that need to be processed raise new questions with respect to efficiency and continuously challenge existing models of computation. Thermal and electrical power constraints have caused technology to reach the power wall with stagnating single processor performance, meaning that all nontrivial applications need to address scalability with multiple processors, a memory hierarchy and other communication challenges. Scalable data structures are pivotal to this process since they form backbone of algorithms driving these applications. The extended abstracts included in this report contain both recent state of art advances and lay foundation for new directions within data structures research.