Databases Flashcards by Jim Owen

Which databases support Read Replicas?

MySQL
MariaDB
PostgreSQL
Aurora

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Which external databases are supported with RDS?

SQL Server
MySQL
Oracle
PostgreSQL

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Can Read Replicas have Multi-AZ enabled?

No, but a source database with Multi-AZ enabled can have Read Replicas

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If a database is restored from either an automated backup or a snapshot, what happens to its end point?

The restored database will be a new RDB instance with a new end point

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What makes Redshift’s advanced compression so efficient?

Because Redshift data is stored in columns, it can be compressed more than traditional databases

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What are database snapshots?

User-initiated backupd of a database which are stored in S3 and retained even if the database is deleted

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What is DynamoDB Reserved Capacity?

Similar to Resered Instances in EC2, it offers discounted throughput capacity for DynamoDB data, when entering into a 1 or 3 year contract.

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Explain Redshift Massive Parallel Processing

Redshift automatically distributes data and query load across all compute nodes. It is easy to add nodes to the warehouse, maintaining fast query performance

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True or false: You can create a Read Replica from another Read Replica

True

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What is Elasticache?

AWS’s in-memory caching service that provides low-latency cahed data for applications that need it, such as recommendation engines, gaming, or social media

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If a database is under a lot of load, what database service would be a good choice to relieve this?

Elasticache

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What is DMS?

Database Migration Service allows you to migrate production database to AWS. AWS manages type transformation, compression and parallel transfer

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If managment is running a lot of OLAP queries on a database, what service is a good choice?

Redshift. Possibly also Read Replicas in RDS

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True or False: A Redshift database can span multiple availability zones

False. Redshift is intended for back office analytics and high performance, so it is not built to span AZs

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True or false: If an RDS is deleted, its database snapshots are retained

True

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What is RDS?

AWS’s Relational Database Service, which allows you to set up, operate and scale relational databases

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How is Redshift encrypted?

In-transit using SSL

At rest using AES-256

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What is Multi-AZ?

It allows you to have an exact syncronous replica of a database in another availability zone. AWS automatically fails over to the replica database if needed

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What is the data consistency model for DynamoDB?

Users can specify whether they want strongly consistent or eventually consistent.

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What is Aurora?

A MySQL-compatible relational database engine, much faster than regular MySQL, much chepaer than commercial databases

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Can existing unencrypted RDS databases become encrypted?

Not directly. To encrypt an existing RDS database, first create a snapshot, copy the snapshot and enable enxryption, then restore the encrypted database

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True or false: Automated backup must be enabled on a database before Read Replcias can be created

True

True or false: Multi-AZ is useful to improve performance of a database

False. Multi-AZ is for disaster recovery only, and does not improve performance

True or false: If an RDS instance is deleted, the automated backups are retained

False

Explain the difference between use of Redshift vs EMR?

Redshift is intended primarily for business intelligence, while EMR is for Big Data processing.

Why would you want to configure DynamoDB with eventual consistency?

Eventual consistency maximized read throughput

How does Aurora achieve fault tolerance?

Automatic replication across three availability zones and automatic failover

what are the relative costs of reads and writes with DynamoDB?

Writes are much more expensive than reads in DynamoDB, which is why it is best used for read-heavy databases

What is the difference between DynamoDB and RDS in terms of scaling?

DynamoDB offers automatic scaling with no down time, while RDS requires use of Read Replicas or manual changes in instance size

What is EMR?

Elastic Map Reduce - It is a service for Big Data processing

True or false: Database snapshots are performed automatically

False. They are user initiated

What is a Read Replica?

An asyncronous, read-only copy of a database

What in-memory caching engines are supported by Elisticache?

Memcached | Redis

Explain the multi-node architecture in Redshift

There is a Leader Node, which manages client connections, received queries, and distributes them to Compute Nodes. Compute Nodes store data and perform queries and computations. This collection of nodes is often called a cluster

How many Read Replicas can you have for a single database?

Describe DynamoDB

A fast and flexible NoSQL database service for applications that need low latency at any scale.

What might be a cause why you are unable to connect to your RDS instance?

You must ensure that the security group allows traffic on port 3306. This can be from an IP, anywhere, or even from another security group

Aurora is compatible with what popular database type?

MySQL

How many Compute Nodes can a Redshift resource have?

128

What are the use cases for Elasticache?

It is intended for read-heavy workloads such as gaming, social media, or compute-heavy workloads such as recommendation engines

What are Automated Backups?

they allow you to recover your database to any point in time within the "retention period"

What is Redshift?

Redshift is a petabyte-scale data warehousing service in the cloud, centered around business intelligence

What is the default retention period for automated backups?

7 days

Can a Read Replica be promoted to be its own source database?

Yes. The replication with the original source will then be broken, however.

What is columnar data storage?

Data is stored sequentially in columns rather than as a series of rows. This greatly reduces amount of I/O for analytical processing. This is also referred to as Dense Storage

How does DynanoDB ensure high availability and durability?

DynamoDB stores three geographically distinct replicas of each table

What are Read Replicas primarily used for?

They can be used to distribute read performance for read-heavy databases

What is an Eventually Consistent Read as applied to DynamoDB?

All copies of data are usually consistent within one second

What are the two different types of database backups in AWS?

Automated backups | Database snapshots

What block size does Redshift use for its columnar storage?

1024Kb - 1Mb

What are the two node types in Redshift?

Dense Storage - uses std HDDs at lower cost | Dense Computer - Uses SSDs for fast processing

What are minimum and maximum storage limits for Aurora?

10Gb minimum, 64Tb maximum, scaled automatically in increments of 10Gb.

How many Read Replicas can Aurora support?

Up to 15

Can you change the RDS DB Instance class after it is created?

Yes