Basics

DynamoDB is a public Database as a Service (DBaas)
It is a key-value & a document store
It is a wide column key-value database
Highly resilient product either across RZs or if configured globally resilient across regions
Data is replicated across multiple storage nodes by default
SSD based providing single digit miliseconds latency
One can define automatic deletion of items in a period by using TTL. A stream can be defined on TTL

Tables

Table is a grouping if items all sharing same primary key
Table can have infinite number of items
A primary key can be
Simple PK or Partition Key only PK
Composite PK i.e. a combination of Partition Key and a Sort Key
An item as zero or more attributes
The total size of an item can not exceed 400 kb which includes primary key, attribute names and attribute values
For provisioned capacity, we need to explicitly set capacity values on per table basis
Capacity is defined in terms of Read Capacity Unit (RCU) & Wri Capacity Unit (WCU)
RCU equals 4kb/s of read. WCU equals 1kb/s of write

Manual backups allow a user to manually full backup , restor it in same or different region, backup with or without indexes and adjust encryptions settings
Point In Time Recovery(PITR) is disabled by default and needs t be enabled on table by table basis
PITR maintains a continuos record of changes over a 35 day period with 1 second granularity