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Eventual Consistency

RDBMSs use a strong transactional/consistency model
  • if a tx commits, changes take effect "instantly"
  • all tx's have a strong guarantee about data integrity
Many new DBMSs applications do not need strong consistency
  • e.g. doesn't matter if catalogue shows yesterday's price
Because of distribution/replication
  • update is initiated on one node
  • different nodes may have different versions of data
  • after some time, updates propagate to all nodes