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DynamoDB

Indroduction​

  • Serverless NoSQL DB with multi-AZ
  • Distributed Database
  • Not an in-memory database (uses storage devices)
  • Storage auto-scaling
  • Single digit millisecond response time at any scale
  • Maximum size of an item: 400 KB
  • Primary key (must be decided at creation) can be a single field or a pair of fields (partition key and sort key)
  • Indexes allow us to query on attributes other than the Primary Key
  • Supports TTL (automatically delete an item after an expiry timestamp)
  • Supports Transactions (either write to multiple tables or write to none)

Capacity​

  • Provisioned Mode (default)
    • Provision read & write capacity
    • Pay for the provisioned capacity
    • Auto-scaling option (eg. set RCU and WCU to 80% and the capacities will be scaled automatically based on the workload)
  • On-demand Mode
    • Capacity auto-scaling based on the workload
    • Pay for what you use (more expensive)
    • Great for unpredictable workloads

DynamoDB Accelerator (DAX)​

  • Caches the queries and scans of DynamoDB items
  • Solves read congestion (ProvisionedThroughputExceededException)
  • Microseconds latency for cached data
  • Doesn't require application code changes
  • 5 minutes TTL for cache (default)

DynamoDB Streams​

  • Ordered stream of notifications of item-level modifications (create/update/delete) in a table
  • Destination can be
    • Kinesis Data Streams
    • AWS Lambda
    • Kinesis Client Library applications
  • Data Retention for up to 24 hours

Global Tables​

  • For low latency access in multiple-regions
  • Applications can READ and WRITE to the table in any region and the change will automatically be replicated to other tables (active-active cross-region replication)
  • Must enable DynamoDB Streams as a pre-requisite