DynamoDB

• Fully managed, highly available with replication across 3 AZs
• NoSQL database - not a relational database
• Scales to massive workloads, distributed database
• Millions of requests per seconds, trillions or rows, hundreds of thousands of TB of storage
• It is fast and consistent regarding performance (low latency retrieval of data)
• It is integrated with IAM for security, authorization and administration
• It enables event driven programming with DynamoDB Streams
• It provides auto scaling capabilities at low cost

Basics

• DynamoDB is made of tables
• Each table has a primary key (must be decided at creation time)
• Each table can have an infinite number of items (rows)
• Each item has attributes which can be added over time (can be null)
• Maximum size of an item is 400KB
• Supported data types:
  • Scalar types: string, number binary, null
  • Document types: list, map
  • Set types: string set, number set, binary set

Provisioned Throughput

• Table must have a provisioned throughput, we must provision read and write capacity units
• Read Capacity Unit (RCU): throughput for reads ($0.00013 per RCU)
  • 1 RCU = 1 strongly consistent read of 4 KB per second
  • 1 RCU = 2 eventually consistent read of 4 KB per second
• Write Capacity Unit (WCU): throughput for writes ($0.00065 per WCU)
  • 1 WCU = 1 write of 1 KB per second
• Option to setup auto-scaling of throughput to meet demand
• Throughput can be exceeded temporarily using burst credits
• If there are no more burst credits, we may get a “ProvisionedThroughputException” in which case it is advised to do exponential back-off retry

DynamoDB - DAX

• DAX = DynamoDB Accelerator
• Seamless cache for DynamoDB, no application re-write
• Write go through DAX to DynamoDB
• Micro second latency for cached reads and queries
• Solves the Hot Key problem (too many reads on one value)
• Each cache entry has a 5 minute TTL by default
• We can get up 10 nodes per cluster for cache
• The cache is multi AZ (3 nodes minimum recommended for production)
• It is secure (Encryption at rest with KMC, VPC, IAM, CloudTrail)

DynamoDB Streams

• Changes in DynamoDB (Create, Update, Delete) can end up in a DynamoDB stream - change log of everything happened in the table
• This stream can be read by AWS Lambda, with which we can do some integrations:
  • React to changes in real time (example: welcome email to new users)
  • Analytics
  • Create derivative tables/views
  • Insert into ElasticSearch
• We can implement cross region replication using Stream
• Streams has 24 hours of data retention

DynamoDB - New Features

• Transactions
  • All or nothing type of operations
  • We can coordinate insert, update and delete operations across multiple tables
  • Include up to 10 unique items or up to 4MB of data per transaction
• On-demand
  • No capacity planning needed (WCU/RCU) - scales automatically
  • It is 2.5x more expensive than provisioned capacity
  • Helpful for spikes and unpredictable loads or if the application has a very low throughput

Security

• We get VPC endpoints to access DynamoDB without internet
• IAM policies
• Encryption at rest using AWS KMS
• Encryption at transit is handled by SSL/TLS
• Backup and restore
  • DynamoDB provides point in time restores (just like any RDS)
  • Backup does not have any performance impact on the tables
• Global tables
  • Multi region, fully replicated, high performance
  • Dynamo provides active-active replication
  • In order to be able to replicate data, DynamoDB Streams should be enabled

Migration

• We can use DMS to migrate data to DynamoDB (from Mongo, Oracle, MySQL, st3, etc.)