Databases Flashcards
How much time does it take a RDS Multi-AZ Replica (Standby Instance) to take over when the Primary has failed?
60-120 seconds, making this not suitable for scenarios where extreme High Availability and Fault Tolerance is required.
Which RDS instance types (Primary, Standby or Read-only) can you access directly, i.e. directly reading/writing from them?
For non-Aurora databases (MySQL, PostgreSQL, MariaDB, Oracle, SQL Server): only Primary and Read-only.
For Aurora: all three, so even the Standby instance.
When deleting a database, which RDS Backup types can be deleted along with the database when selecting the corresponding option? Automatic Backups, Manual Snapshots, or both?
Only Automatic Backups
What’s the maximum retention period for RDS Automatic Backups?
35 days
At which intervals does RDS save Transaction Logs to S3?
5 minutes
What’s the max. number of direct read-replicas per RDS DB instance?
5
How many copies of the underlying storage does Amazon Aurora hold, and across how many AZs are these distributed?
6 copies, split over 3 AZs
What’s the max. number of read-replicas per RDS DB instance when using Aurora?
15
What’s the difference between Aurora and non-Aurora instances when it comes to the Ready-only Instances endpoints?
Aurora provides a single endpoint for Read-only instances and load-balances, allowing to provision new Read-only instances without any configuration changes required. With Non-Aurora instances there will be new endpoint addresses instead as each instance has it’s own address.
What’s the max. size for an item in DynamoDB?
400 KB
What is the data size for a single WCU in DynamoDB?
1 KB
What is the data size for a single RCU in DynamoDB?
4 KB
How many days is the recovery window with DynamoDB (i.e. how many days back does DynamoDB allow you to restore a database to any given second)?
35 days
Which DynamoDB index type can be created only at table creation time?
Local Secondary Index (LSI)
Which DynamoDB index type can be created after a table was already created?
Global Secondary Index (GSI)
What’s the max. number of Local Secondary Indexes (LSI) with DynamoDB?
5
Which DynamoDB index type shares RCU and WCU with the table?
Local Secondary Index (LSI)
What’s the max. number of Global Secondary Indexes (LSI) with DynamoDB?
20
Which DynamoDB index type can use an Primary Key & Sort Key that is different from that of the table?
Global Secondary Index (GSI)
Which DynamoDB index type must use the same Primary Key as the table (but can use a different Sort Key)?
Local Secondary Index (LSI)
Which DynamoDB index type has it’s own RCU and WCU allocation?
Global Secondary Index (GSI)
Which DynamoDB index type is always eventually consistent? And why?
Global Secondary Index (GSI) as they’re replicated asynchronously.
What are the most common supported OLTP databases supported by the Schema Conversion Tool (SCT)?
MySQL/MariaSQL, MSSQL, Oracle, DB2, PostgreSQL
What are the most common supported OLAP databases supported by the Schema Conversion Tool (SCT)?
Redshift, Oracle DWH, Teradata, Greenplum, Vertica, MSSQL Server
Given a 5 GB table in DynamoDB, that uses 2000 RCU and WCU, what’s the number of partitions that DynamoDB will use?
Calculate partitions by size and capacity as follows, then take the rounded, upper value of both.
Formulas:
- Capacity: (Total RCU / 3000) + (Total WCU / 1000)
- Size: Total size / 10 GB
For this example: - Capacity: (2000 / 3000) + (2000 / 1000) = 2.67 - Size: 5 GB / 10 GB = 0,5 Max(2.67, 0,5) = 2.67 Rounded(2.67) = 3 ==> 3 Partitions
When performing an automatic failover, what DNS record is modified by RDS, and from which value to which other value is it changed?
CNAME is changed from primary to standby instance’s address.
What database engines are available for Amazon Aurora Serverless v1?
MySQL and PostgreSQL
What database engines are available for Amazon Aurora Serverless v2?
MySQL only
What are the key differences between Amazon Aurora Serverless v1 and v2?
v1 is cheaper, but takes longer to scale up/down, cannot scale/up down in small increments (always doubles/halves) and does not support important features such as Global Database, Back Tracking, Multi-AZ deployments, and read replicas.
v2 though doesn’t support PostgreSQL yet, which v1 does.
What’s the product name of Aurora for it’s feature that allows a single Amazon Aurora database to span multiple AWS regions?
Aurora Global Database
What’s the product name of DynamoDB’s feature that replicates your DynamoDB tables automatically across your choice of AWS Regions?
DynamoDB Global Tables
Can you use ElastiCache with RDS, DynamoDB, or both?
Both
