DynamoDB Quick Notes (Numbers)

Submitted by heartin on Sun, 03/04/2018 - 13:29

DynamoDB is very important for clearing AWS Certified Developer Associate.

Quick Notes (Numbers)

DynamoDB synchronously replicates data across three facilities in an AWS Region.
DynamoDB Streams captures a time-ordered sequence of item-level modifications in any DynamoDB table, and stores this information in a log for up to 24 hours.
In DDB, the total value of an item (including all attribute names and values) cannot exceed 400KB.
For any AWS account, there is an initial limit of 256 tables per region. This may be changed contacting AWS.
Names for tables and secondary indexes must be at least 3 characters long, but no greater than 255 characters long.
Attribute names must be encoded using UTF-8, and the total size of each name (after encoding) cannot exceed 255 bytes.
The minimum length of a partition key value is 1 byte. The maximum length is 2048 bytes.
The minimum length of a sort key value is 1 byte. The maximum length is 1024 bytes.
For tables with local secondary indexes, for every distinct partition key value, the total sizes of all table and index items cannot exceed 10 GB.
You can create upto 5 GSI and 5 LSI.
A single Query response has a size limit of 1 MB.
A BatchGetItem request can retrieve upto 16 MB of data. Contain upto 100 items.
DynamoDB Free Tier. 25 write capacity units and 25 read capacity units. 25 GB of indexed data storage. 2.5 million read requests per month from DynamoDB Streams.
Reserved Capacity applies within a single Region and can be purchased with 1-year or 3-year terms.
You can add up to 50 tags to a single DynamoDB table.
One write capacity unit (WCU) provides up to one write per second.
One read capacity unit (RCU) provides. two reads per second for eventual consistency reads. one read per second for strongly consistent reads.
You can decrease the ReadCapacityUnits or WriteCapacityUnits settings for a table (UpdateTable operation) up to four times any time per day.
If there was no decrease in the past four hours, an additional dial down is allowed, effectively bringing maximum number of decreases in a day to nine times (4 decreases in the first 4 hours, and 1 decrease for each of the subsequent 4 hour windows in a day).
All reads are rounded upto 4 KB. 8 KB will require two units.
All writes are 1 KB.
For any table or global secondary index, the minimum settings for provisioned throughput are 1 read capacity unit and 1 write capacity unit.
For tables with secondary indexes, only one of those tables can be in the CREATING state at any point in time.
For tables with secondary indexes, total limit of tables in the ACTIVE state is 250.
Each table can have up to 20 projected non-key attributes, in total across all local secondary indexes within the table.
Updating items with an older TTL values is allowed. However, if the value is over 5 years old, DynamoDB will ignore the timestamp and not delete the item.
A unit of read capacity represents one strongly consistent read per second or two eventually consistent reads per second.