DynamoDB

• Fully managed service
• Is made of tables (no need to create databases)
• Each table must have a primary key (decided at creation time)
• Each table can have an infinite items (rows)
• Each item have attributes (can be added over time, can be null)
• Maximum size of item is 400KB
• Supported data types:
  • Scalar types: String, Number, Binary, Boolean, Null
  • Document Types: List, Map
  • Set Types: String set, Number Set, Binary Set

Primary Keys

• Option 1: Partition key only (Hash)

  • Partition Key must be unique for each item
  • Partition Key must be diverse so that the data is distributed

• Option 2: Partition Key + Sort Key

  • The combination must be unique
  • Data is grouped by partition key
  • Sort == range key

Anti-Pattern

• Pre-written application to traditional relational database => use RDS instead

• Joins or complex transactions

• Binary Large Object (BLOB) => Store in S3 & metadata in DynamoDB

• When you create table in DynamoDB you must provide:

1. Read Capacity Units: throughput for reads
   • How we compute it ?
   • Once write capacity unit: represents one write per second for an item up to 1KB in size

• Write Capacity Units: throughput for writes

Partitions

• You start with one partition

• Each partition:

  • Max of 3000 RCU / 1000 WCU
  • Max of *10GB

• To compute the number of partitions:

  • By capacity => (TOTAL RCU / 3000) + (TOTAL WCU / 1000)
    • By size => (TOTAL table size / 10 BG)
  • Total partitions = CEILING(MAX(Capacity, Size))

• WCU and RCU are spread evenly between partitions

Auto Scaling