Databases

Question 1

DynamoDB

Answer 1

• Fully managed, nosql, massive scale (1000000 rps)
• Max object size 400KB
• Capacity provisioned (WCU, RCU & autoscaling) or on-demand
• Reads can be eventually or strongly consistent
• Supports transactions across multiple tables (ACID)
• Backups and point-in-time recovery available
• Integrated with IAM for security

Question 2

DynamoDB - Primary Keys

Answer 2

• Must be unique
• Partition key only
• Partition key + sort key
• • Data grouped by partition key, the timestamp is an example of the good sort key

Question 3

DynamoDB - Indexes

Answer 3

• In order to query an attribute must create an index of it
• LSI - Local Secondary Index
• • Same partition key, the alternative sort key
• • Must be added at creation
• GSI - Global Secondary Index
• • Different partition and sort key
• • Can be defined after the table creation
• • Needs provisioned throughput per index, extra $

Question 4

DynamoDB - TTL

Answer 4

Can expire rows

Question 5

DynamoDB - Streams

Answer 5

• React to change in tables in real time
• 24-hour retention
• Can send to lambda, sqs, sns, ec2 and more

Question 6

DynamoDB - Global Tables

Answer 6

• Active Active xregion replication, many regions
• Must enable streams
• Good for low latency, DR

Question 7

DynamoDb - DAX

Answer 7

• DynamoDB Acceleration, aka cache
• No application code, directly integrated with DynamoDB
• Good for handling hot key problem
• 5 min TTL by default
• Multi AZ, recommended min 3 node for PROD
• Secure (KMS, IAM, VPC, CloudTrail)
• Up to 10 nodes in the cluster

Question 8

Amazon ElasticSearch (ES)

Answer 8

• Not serveless, need to provision servers

- Must specify instance types, must be Multi-AZ

Question 9

ElasticSearch + DynamoDB

Answer 9

Searching + Fast key-value store and retrieval

Store in Elasticsearch using streams and lambda

Question 10

ES + CW

Answer 10

cw + subscription filter + lambda + es - real time
cw + subscription filter + kinesis + es - near real time

build own analytics and dashboard using kibana

Question 11

RDS

Answer 11

• PostgreSQL, MySQL, MariaDB, Oracle, MS SQL Server

- Managed but requires provisioned servers

Question 12

RDS VPC

Answer 12

Must be in VPC in private subnet, access controlled using SGs

Question 13

RDS Storage

Answer 13

EBS (gp2 or io1), can enable auto-scaling

Question 14

RDS Recovery

Answer 14

• Automated backups, pit recovery. Backups expire.

- Snapshots manual, can make copies of snapshots xregion

Question 15

RDS Events

Answer 15

• Get notified via SNS about operations, outages, backups etc

Question 16

RDS Multi AZ

Answer 16

• Master + Standby (Sync replication)
• One dns name
• Reads/writes only to master
• In case of failover, dns automatically will failover to standby

Question 17

RDS Read Replicas

Answer 17

• Increase Read throughput
• Eventual consistency, so async replication to read replicas
• Can be xregion

Question 18

Aurora

Answer 18

• PostgreSQL and MySQL

- Backup/restore/snapshot same as RDS

Question 19

Aurora Storage

Answer 19

• Automatically grows in 10GB increments up to 64TB
• 6 copes of data across 3 AZ
• 4 out of 6 needed for writes
• 3 out of 6 needed for reads

Question 20

Aurora Replication

Answer 20

• Up to 15 RR with Read endpoint to access them all
• Xregion replication, entire database (Unlike DynamoDb)
• Self-healing with Peer to Peer replication

Question 21

Aurora + S3

Answer 21

• Efficiently load/offload to/from S3

Question 22

Aurora Master

Answer 22

• Can failover within 30 seconds

- Can write only to master, using writer endpoint