DB

Question 1

Row Store

Answer 1

Stores data in rows

Good for Transactional DB. OLTP

This is important if the Data will be queried (CRUD) for all rows at once at all times. Eg, Sales record.

Example AWS: ** MySQL

Question 2

Column Store

Answer 2

Columns are stored together. Ideal for reporting or when all values for a specific attribute (size) are required.

OLAP
- This is good for Inventories and reporting.
- Data warehouse
- Analytics

You can take data from an OLTP into a Column store for reporting and analytics

eg AWS: REDSHIFT

Question 3

Graph DB

Answer 3

Data, alongside their relationships, are stored in the DB, hence querying the data returns results really fast.

Best for systems with complex sophisticated Relationships

Question 4

Justifications for DB on EC2

Answer 4

• Access to the DB Instance OS
• Advanced DB Option tuning … (DBROOT)
• … Vendor demands..
• DB or DB Version AWS don’t provide..
• Specific OS/DB Combination AWS don’t provide
• Architecture (AWS don’t provide replication/resilience)
• Decision makers who ‘just want it’

Question 5

DB on EC2 CONS

Answer 5

• Admin overhead - managing EC2 and DBHost
• Backup / DR Management
• EC2 is single AZ
• Features - some of AWS DB products are amazing
• EC2 is ON or OFF - no serverless, no easy scaling
• Replication - skills, setup time, monitoring & Effectiveness
• Performance….AWS invests time into optimisation & features

Question 6

Command to migrate a mysQl DB into a file

Answer 6

$ mysqldump -u root -p alwordpress > a41wordpress.sql

Question 7

RDS

Answer 7

RDS is a VPC service. It is deployed into a subnet

Question 8

RDSMulti-AZ Deployment

Answer 8

Without indication, in a Multi-AZ setup, RDS will randomly select any two subnets in two AZs for its deployment; one for its Primary, and the other, standby DB, all within its Subnet Group

Question 9

RDS Instance Architecture

Answer 9

An RDS Instance can have more than one Database on them

Every RDS Instance (Master and Standby) has its own dedicated EBS Storage

AWS
Note that RDS for SQL Server has a limit of up to 100 databases on a single DB instance.

Question 10

RDS Replication

Answer 10

Synchronous: Data is replicated to standby as soon as it arrives.

Read Replicas are Asynchronously replicated. This can be same AZ, Multi AZ, or Multi Region.

Read replicas are used to create resilience, HA , and to scale read workloads.

Question 11

RDS Backup

Answer 11

In Multi Az mode, backup happens on the standby instance, hence, extremely short downtime

Question 12

RDS Free Tier

Answer 12

Single AZ

Question 13

Functions of the RDS Standby Instance

Answer 13

For Failover Only
And then Backups to S3

Question 14

RDS Failover notable events

Answer 14

DB CNAME changes from the Primary DB Endpoint to the Standby Endpoint Url.

Failover to a Standby can take up to 60s-120s. This is to enable DNS Endpoint swapping

Question 15

RDS Multi AZ Cluster vs Multi Az instance

Answer 15

• Multi AZ instance deploys a Primary DB, and a standby in another AZ.
• **No operation is allowed on the standby apart from Automatic Failover.

while

• Multi AZ Cluster deploys a Primary Master and two or more RR is different AZs.
• Multi AZ Cluster runs on faster Hardware (Graviton + NVME SSD storage).
• Read replicas can be promoted to Primary
• All RRs are read-active
• Faster Failover (35s)

Question 16

RDS Consistency model

Answer 16

RDS data is considered Confirmed after Main and Standby/RR are committed

Question 17

RDS Backup

Answer 17

• Manual Snapshots
• Automated Backup
  both are stored on AWS Managed S3 Bucket; Bucket is not available for user Access.

Question 18

RDS Snapshot

Answer 18

• Causes time-out on a Single AZ deployment
• Do not expire
• More frequent snapshots=Faster RTO
• After initial Snapshot, subsequent snapshots are incremental.
• Snapshots dont Expire. They Have to be deleted Manually or via some external process

Question 19

Automated Backup content

Answer 19

Automated snapshots contains DB data, and Transaction logs(5min granularity)

Automated backups takes place once a day, during the backup window.

Question 20

Backup retention

Answer 20

0 days - No Backup
35days - Max

Question 21

RDS Restore (Snapshot/Backup)

Answer 21

During RDS Restore, RDS Deploys a brand new DB, hence Applications need to be updated with the new endpoint.

• Snapshots are restored to its Backup point in time
• Automated Backups are restored to any 5mins Point in time. Backup is restored and transaction logs are ‘replayed’ to bring DB to desired point in time (GOOD RPO)

Question 22

RDS Restore RTO

Answer 22

• RDS Restore time is not short. It takes time

Depending on the amount of data on the DB

Question 23

RDS Read Replica

Answer 23

They are eventually consistent. and have their own separate endpoint.

Without Application support, RR are useless.

RR do not perform Automatic failover.

Once Cross-Region is selected, AWS Handles the Networking.

Note: Synchronous - Multi AZ
Asynchronous: Read Replica

Question 24

RDS Encryption

Answer 24

• Authentication
• Authorization
• Encryption In Transit
• Encryption at rest

Question 25

Is it good to store images in relational database?

Answer 25

Storing binary files in a relational database is not very efficient. The process of saving and retrieving the files from a database is generally much slower than using file storage.

Question 26

RDS as a managed service

Answer 26

RDS is managed, hence, ssh is not allowed