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AWS > Databases > Flashcards

Databases Flashcards

1
Q

How much time does it take a RDS Multi-AZ Replica (Standby Instance) to take over when the Primary has failed?

A

60-120 seconds, making this not suitable for scenarios where extreme High Availability and Fault Tolerance is required.

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2
Q

Which RDS instance types (Primary, Standby or Read-only) can you access directly, i.e. directly reading/writing from them?

A

For non-Aurora databases (MySQL, PostgreSQL, MariaDB, Oracle, SQL Server): only Primary and Read-only.
For Aurora: all three, so even the Standby instance.

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3
Q

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?

A

Only Automatic Backups

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4
Q

What’s the maximum retention period for RDS Automatic Backups?

A

35 days

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5
Q

At which intervals does RDS save Transaction Logs to S3?

A

5 minutes

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6
Q

What’s the max. number of direct read-replicas per RDS DB instance?

A

5

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7
Q

How many copies of the underlying storage does Amazon Aurora hold, and across how many AZs are these distributed?

A

6 copies, split over 3 AZs

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8
Q

What’s the max. number of read-replicas per RDS DB instance when using Aurora?

A

15

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9
Q

What’s the difference between Aurora and non-Aurora instances when it comes to the Ready-only Instances endpoints?

A

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.

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10
Q

What’s the max. size for an item in DynamoDB?

A

400 KB

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11
Q

What is the data size for a single WCU in DynamoDB?

A

1 KB

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12
Q

What is the data size for a single RCU in DynamoDB?

A

4 KB

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13
Q

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)?

A

35 days

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14
Q

Which DynamoDB index type can be created only at table creation time?

A

Local Secondary Index (LSI)

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15
Q

Which DynamoDB index type can be created after a table was already created?

A

Global Secondary Index (GSI)

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16
Q

What’s the max. number of Local Secondary Indexes (LSI) with DynamoDB?

A

5

17
Q

Which DynamoDB index type shares RCU and WCU with the table?

A

Local Secondary Index (LSI)

18
Q

What’s the max. number of Global Secondary Indexes (LSI) with DynamoDB?

A

20

19
Q

Which DynamoDB index type can use an Primary Key & Sort Key that is different from that of the table?

A

Global Secondary Index (GSI)

20
Q

Which DynamoDB index type must use the same Primary Key as the table (but can use a different Sort Key)?

A

Local Secondary Index (LSI)

21
Q

Which DynamoDB index type has it’s own RCU and WCU allocation?

A

Global Secondary Index (GSI)

22
Q

Which DynamoDB index type is always eventually consistent? And why?

A

Global Secondary Index (GSI) as they’re replicated asynchronously.

23
Q

What are the most common supported OLTP databases supported by the Schema Conversion Tool (SCT)?

A

MySQL/MariaSQL, MSSQL, Oracle, DB2, PostgreSQL

24
Q

What are the most common supported OLAP databases supported by the Schema Conversion Tool (SCT)?

A

Redshift, Oracle DWH, Teradata, Greenplum, Vertica, MSSQL Server

25
Q

Given a 5 GB table in DynamoDB, that uses 2000 RCU and WCU, what’s the number of partitions that DynamoDB will use?

A

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
26
Q

When performing an automatic failover, what DNS record is modified by RDS, and from which value to which other value is it changed?

A

CNAME is changed from primary to standby instance’s address.

27
Q

What database engines are available for Amazon Aurora Serverless v1?

A

MySQL and PostgreSQL

28
Q

What database engines are available for Amazon Aurora Serverless v2?

A

MySQL only

29
Q

What are the key differences between Amazon Aurora Serverless v1 and v2?

A

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.

30
Q

What’s the product name of Aurora for it’s feature that allows a single Amazon Aurora database to span multiple AWS regions?

A

Aurora Global Database

31
Q

What’s the product name of DynamoDB’s feature that replicates your DynamoDB tables automatically across your choice of AWS Regions?

A

DynamoDB Global Tables

32
Q

Can you use ElastiCache with RDS, DynamoDB, or both?

A

Both

AWS (16 decks)

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