Limitations of highly-available eventually-consistent data stores

Hagit Attiya, Faith Ellen, Adam Morrison

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


Modern replicated data stores aim to provide high availability, by immediately responding to client requests, often by implementing objects that expose concurrency. Such objects, for example, multi-valued registers (MVRs), do not have sequential specifications. This paper explores a recent model for replicated data stores that can be used to precisely specify causal consistency for such objects, and liveness properties like eventual consistency, without revealing details of the underlying implementation. The model is used to prove the following results: An eventually consistent data store implementing MVRs cannot satisfy a consistency model strictly stronger than observable causal consistency (OCC). OCC is a model somewhat stronger than causal consistency, which captures executions in which client observations can use causality to infer concurrency of operations. This result holds under certain assumptions about the data store. Under the same assumptions, an eventually consistent and causally consistent replicated data store must send messages of unbounded size: If s objects are supported by n replicas, then, for every k > 1, there is an execution in which an (minfn; sgk)-bit message is sent.

Original languageEnglish
Title of host publicationPODC 2015 - Proceedings of the 2015 ACM Symposium on Principles of Distributed Computing
PublisherAssociation for Computing Machinery
Number of pages10
ISBN (Electronic)9781450336178
StatePublished - 21 Jul 2015
Externally publishedYes
EventACM Symposium on Principles of Distributed Computing, PODC 2015 - Donostia-San Sebastian, Spain
Duration: 21 Jul 201523 Jul 2015

Publication series

NameProceedings of the Annual ACM Symposium on Principles of Distributed Computing


ConferenceACM Symposium on Principles of Distributed Computing, PODC 2015
CityDonostia-San Sebastian


  • Causal consistency
  • Eventual consistency
  • Replicated data store


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