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State-of-the-art fault-tolerant and federated data management systems rely on fully-replicated designs in which all participants have equivalent roles. Consequently, these systems have only limited scalability and are ill-suited for high-performance data management. As an alternative, we propose a hierarchical design in which a Byzantine cluster manages data, while an arbitrary number of learners can reliable learn these updates and use the corresponding data. To realize our design, we propose the delayed-replication algorithm, an efficient solution to the Byzantine learner problem that is central to our design. The delayed-replication algorithm is coordination-free, scalable, and has minimal communication cost for all participants involved. In doing so, the delayed-broadcast algorithm opens the door to new high-performance fault-tolerant and federated data management systems. To illustrate this, we show that the delayed-replication algorithm is not only useful to support specialized learners, but can also be used to reduce the overall communication cost of permissioned blockchains and to improve their storage scalability.
@InProceedings{hellings_et_al:LIPIcs.ICDT.2020.17,
author = {Hellings, Jelle and Sadoghi, Mohammad},
title = {{Coordination-Free Byzantine Replication with Minimal Communication Costs}},
booktitle = {23rd International Conference on Database Theory (ICDT 2020)},
pages = {17:1--17:20},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-139-9},
ISSN = {1868-8969},
year = {2020},
volume = {155},
editor = {Lutz, Carsten and Jung, Jean Christoph},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2020.17},
URN = {urn:nbn:de:0030-drops-119418},
doi = {10.4230/LIPIcs.ICDT.2020.17},
annote = {Keywords: Byzantine learner, coordination-free checkpoint protocol, delayed-replication, information dispersal, consensus}
}