Database Flashcards by Mark Sarge

What are the DB Instance Types?

M (Multipurpose)
R (RAM / Memory)
T (Tiny / Burstable)

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What are the Aurora features for automatic reliability?

Storage Auto Repair (detects failing discs)
“Survivable” cache warming (separate process to warm cache)
Crash Recovery (almost instant recovery

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What are the three security levels for Aurora?

IAM
Security Groups
Database Authentification

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What are the three storage types?

Magnetic, General Purpose & Prov. IOPS

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When does RDS automatically fail over?

Loss of AZ
Loss of network connectivity to primary instance
Compute unit failure on primary instance
Storage failure on primary instance

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How to enable Multi-AZ on RDS?

It can be created new or as a modification

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What to consider for read replicas?

Automated backup must be enabled
Cannot be used behind an ELB
Can be promoted to primary, will break the replication
Up to 5 RRs (mysql/postgres)
Up to 15 RRs for Aurora
Multi Region for mysql, postgres & aurora
Database snapshots cannot be made from RRs

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How is the failover process for RDS structured?

Automatically, needs 60-120s (more for large DBs)

It changes the DNS endpoint

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What is RDS Snapshot Copy?

Possibility to copy snapshots to any public Region

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How are automatic snapshots generated?

Daily in the backup window. I/O can be reduced in that time.

It cannot overlap with the weekly maintenance window.

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How to scale up in a Multi-AZ environment?

First the Standby will be upgraded, then there’s a minimal downtime when the primary is scaled

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What is Sharding?

Horizontal partitions

Seperate instances that contain a subset of the whole dataset

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What can be be monitored in RDS?

CPU/RAM/Disk space consumptions
Network traffic
Database connections
IOPS metrics

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Dynamo DB: What is an item?

Group of attributes that can be uniquely identified from all other items

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Dynamo DB: How are RCU calculated?

One read capacity: 1 strongly consistent read or 2 eventually consistent read of 4KB

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Dynamo DB: How are WCU calculated?

1KB in size = 1 WCU

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Dynamo DB: What is Reserved Capacity?

Reserving RCU/WCU for a fee, which reduces the cost of the IOPS

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DynamoDB: How do indicies affect WCU?

Every WCU scales with the amount of indices.
1 primary: 1KB
1 primary + index: 2KB

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DynamoDB: What happens when the prov. throughput is exceeded?

It fails with a 400 code.

AWS SDK have an automatic retry.

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What is the benefit of a VPC endpoint?

no need for internet of NAT
no need for additional firewalls
no additional costs

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Redshift: What is the purpose of the leader node?

It receives the queries, parses them and develops execution plan

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What is the maximum number of data copies that Amazon Aurora can lose without affecting writes?

Amazon Aurora at maximum can withstand the loss of two copies of data without affecting writes

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What CloudWatch metric is used to determine needs for storage type changes?

ReadIOPS/WriteIOPS is a metric used to determine a need for storage type changes.

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What are two of the available node types for Amazon ElastiCache of the current generation?

Memory Optimized & General Purpose

What needs to be done when a RDS failover occurs.

Nothing, the connection endpoint will stay the same.

What is Replication Lag?

The time it takes for the RR to include the most current data

What is the requirement for enabling Read Replicas?

Enable automated backups

Can you create an read replica of a read replica?

Yes, but here also automated backups need to be enabled for the original RR as well

How to use an existing database for testing?

Promote a read replica as master - therefore you now have two databases in parallel

How to encrypt an existing database?

Take a snapshot Copy the snapshot in the same or different region with encryption enabled Create a database

How to share an encrypted RDS Snapshot with another account?

- Create a custom (not the default) KMS Key and share it with the other account - Encrypt the database with that key

Which ElastiCache engine supports Multi-AZ?

Redis

RDS: How to scale?

Increase the size. (Scaling up) | It is not possible to scale out RDS

RDS: What are the benefits of Multi-AZ?

- High availability (failover) - Backups are taken from the standby - Restores are taken from the standby

RDS: What happens when a Read Replica is created?

AWS takes a snapshot of the data (from the primary, o r the secondary if Multi AZ is enabled)

RDS: What are the restriction to share an encrypted RDS Snapshot?

- Cannot be encrypted with the default KMS Key - Cannot be shared public -

RDS: What is Aurora Serverless?

Automatically scaling database, where you are paid by the second of usage. Very like Lambda.

Which CLI command can you use to determine which version of RDS you are using?

describe-db-instances

DynamoDB: How to use scheduled provisioning?

It is not possible to scale on a schedule, use auto-scaling instead

You need to check the OS of the instances to ensure that the latest patches are installed and that the proper security requirements are being met. What AWS service could you use to complete your task?

Check maintenance of the instances on the Amazon RDS console.

RDS: What are the two methods of backups?

point-in-time-recovery: database and transaction backup - allows to jump to a certain point in time. Is stored for 35 days DB Snapshots: Full database backup. Can be moved to another region and also used to create a new database

RDS: How to avoid I/O suspension on backups

Use Multi-AZ

Redshift: What happens, when a drive fails?

It is automatically replaced

Redshift: What is an Audit Log?

Stores all SQL operations, such as login attempts, queries or changes to the database

Which service can be used to migrate a database?

AWS Database Migration Service

How does DynamoDB provide HA and high performance?

HA: It automatically replicates data to multiple AZs in a region. Performance: It generates more partitions and provisions more server capacity if the table grows or mote throughput is needed

What affects I/O?

Snapshot creation Backups Read Replica creation Scaling storage

RDS: Is it possible to create a Multi-.AZ setup after database creation?

yes

RDS: What is RDS Snapshot Copy?

Possibility to copy snapshots to different regions. | Is a copy already exists only the storage delta is transferred

What is a DynamoDB Stream?

Metadata about every create, update or delete on the table

DynamoDB: What function is called for a single item or multiple items?

single: GetItem multiple: BatchGetItem

What would you call databases in a NoSQL implementation?

In a NoSQL implementation, databases are referred to as stores, and there are four types of stores: document, graph, key/value, and wide column.

Which type of NoSQL store is optimized for querying really large datasets?

Wide column stores

What is the (soft) limit for RDS database?

When would it be okay to disable automated backups?

When you are loading a large amount of data.

RDS: When must the decision to encrypt a database be made? on creation or any time?

on creation.

RDS: . What would be the best solution to | enable messages related to changes with your RDS clusters?

Amazon RDS events

Which on is asynchronous, which one is synchronous? | Read-Replica, Multi AZ

Read-Replica: asynchronous | Multi AZ: synchronous