DynamoDB Flashcards
What is AWS DynamoDB?
DynamoDB is a fast and flexible NoSQL DB service for all applications that need consistent, single-digit milliscond latency at any scale
Does DynamoDB support document data models?
Yes
Does DynamoDB support key-value data models?
Yes
Where is DynamoDB data stored?
On SSD storage
How does Dynamo DB provide data redundancy?
Data in DynamoDB is spread across 3 geographically distinct data centers
What is the data consistency model for DynamoDB?
Eventually Consistent Reads by Default
Strongly Consistent Reads as an option
Roughly when are Eventually Consistent Reads consistent?
Data consistency is usually reached within 1 second
What are Strongly Consistent Reads?
A strongly consistent read reflects all writes that received a successful response prior to the read.
What does DAX stand for?
DynamoDB Accelerator
What is AWS DAX?
Fully managed, highly-available in-memory cache for DynamoDB
What is the performance improvement offered by AWS DAX?
10x performance improvement over DB standalone
Reduces request time from milliseconds to microseconds
What does the developer need to do to manage the logic in AWS DAX?
Nothing. The caching logic is fully managed by AWS
Can AWS DAX also provide write speedup?
Yes, it is a write-through cache
What does DynamoDB Transactions assist with?
Atomic operations
(Think money transfer, can’t debit one account without crediting another)
How does using DynamoDB Transactions affect read/write capacity?
Transactions does 2 underlying reads or writes of every item in the transaction, one to prepare, and one to commit.
What is DynamoDB On-Demand Capacity?
Pay-per-request pricing
What is the minimum capacity required for DynamoDB On-Demand capacity?
There is none!
What is the pricing model for DynamoDB On-Demand Capacity?
- No charge for read/write while the table is idle, only for storage and backups
- Pay more per request than with provisioned capacity
What is the recommended use case for DynamoDB On-Demand Capacity?
New Product Launches, when you don’t have a sense ahead of time of how much traffic to expect
What is the maximum amount of data on which DynamoDB Transactions can operate at any time?
25 items or 4MB of data
What is the performance hit of AWS DynamoDB On-Demand Backup and Restore?
There is zero impact on table performance
What is the availability hit of using DynamoDB On-Demand Backup & Restore?
There is zero impact on table availability
What is the data consistency model for DynamoDB On-Demand Backup and Restore?
Data is consistent within seconds
What is the data retention model for DynamoDB On-Demand Backup & Restore?
Data is retained until deleted
Can you have a DynamoDB On-Demand Backup in the same region as the source table?
Yes
Can you have a DynamoDB On-Demand Backup in a different region from your source table?
No
What does PITR stand for?
Point-In-Time Recovery
What is the purpose of DynamoDB PITR?
To protect against accidental writes and deletes
How far back can you restore using PITR?
Restore to any point in the last 35 days
How is DynamoDB backup data stored?
DynamoDB keeps incremental backups of your data
Is DynamoDB PITR enabled by default?
No
With DynamoDB PITR, how far back is the latest restorable time stamp?
Typically 5 minutes in the past
What is a DynamoDB Stream?
A time-ordered sequence of item-level changes in a table
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How long is info stored in DynamoDB Stream?
Info is stored for 24 hours
If you wanted to imitate a stored procedure functionality in Dynamo DB, how might you do it?
Combine Streams with AWS Lambda Functions
What does DMS stand for?
Database Migration Service
What are some of the ways you can get security in DynamoDB?
- Encryption at Rest (with KMS)
- site-to-site VPN
- Direct Connect
- IAM Policies & Roles (or fine-grained access)
- mornitoring using CloudWatch and CloudTrail
- VPC endpoints
How is data in DynamoDB stored?
It is stored in JSON Format
What is the maximum allowed item size in DynamoDB?
The key and value combined can be at most 400KB
Which storage service is best for storing object metadata?
DynamoDB