AWS Consistency Models

S3 Consistency Model

  • Puts (New record) = Read-after-write consistency model
  • Updates and Deletes = Eventual consistency model

DynamoDB Consistency Model

  • Write = Eventual consistency model
  • Read = Eventual consistency model
  • Read  = Optional – Strong consistency model

Definitions

  • Read-after-write consistency model = New objects should be available with out delays to clients.
  • Eventual consistency model = “Eventually” all access attempts to a particular item will return the last updated value.  There is potential here for stale or old data reads while data replication occurs.
  • Strong consistency model = All access attempts (e.g. parallel) to a particular item return the same unique state.  Old\stale data reads are avoided, but it will cost you more.

Good information to know for any AWS certification tests…. 🙂

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