RDS + Aurora + ElastiCache

Question 1

What is Amazon RDS?

Answer 1

Managed DB service for DB using SQL as query language

Question 2

RDS Storage Auto Scaling

Answer 2

When RDS detects you are running out of free database storage, it scales automatically (set maximum storage threshold limit for maximum DB storage), good for unpredictable workloads

Question 3

RDS Read Replicas

Answer 3

read-only copies of a primary database instance, used to offload read-heavy workloads and improve database performance (only for reading, not updating, as it is async)

Question 4

RDS Read replica use case

Answer 4

Team wants to run reporting application on the prod DB but don’t want to slow prod DB down

Question 5

RDS Read Replicas network costs

Answer 5

same region/different AZ does not incur a cost but cross region does

Question 6

RDS Multi AZ (disaster recovery)

Answer 6

SYNC replication of DB to standby database to increase the availability, resistant to loss of AZ or network or storage failure

Question 7

Can Read Replicas be set up as Multi AZ for disaster recovery?

Answer 7

Yes

Question 8

How to make RDS from single AZ to multi AZ?

Answer 8

Zero downtime operation (don’t need to stop DB), just click on modify for the DB to create standby DB

Question 9

Amazon Aurora

Answer 9

Proprietary DB from AWS, cloud optimised, automatically grows in increments of 10GB

Question 10

Aurora DB Cluster Writer Endpoint

Answer 10

Points to the master (as only master writes to DB)

Question 11

Aurora DB Cluster Reader Endpoint

Answer 11

Connects to all read replicas for connection load balancing

Question 12

At rest encryption

Answer 12

Data is encrypted on the volumes

Question 13

In flight encryption

Answer 13

encryption between client and DB

Question 14

Can you use IAM authentication for accessing DB?

Answer 14

yes

Question 15

Does RDS and Aurora have SSH access?

Answer 15

no (except for custom RDS)

Question 16

Amazon RDS proxy

Answer 16

improves DB efficiency by reducing stress on database resources and minimizing open connections by pooling connections

Question 17

How do you enforce IAM auth for your database?

Answer 17

Use Amazon RDS proxy, enable IAM auth, store credentials in AWS secrets manager

Question 18

Amazon ElastiCache

Answer 18

Helps reduce load off DBs for read intensive workloads by caching

Question 19

What is a cache hit?

Answer 19

Query has already been made and it is stored in the cache

Question 20

What is Redis?

Answer 20

Multi AZ with auto failover, read replicas to scale reads and have high availability, backup and restore reatures

Question 21

What is Memached?

Answer 21

Multi node for partitioning of data, no high availability (read replica), backup and restore only for serverless

Question 22

When is it good to cache data?

Answer 22

Data changing slowly, few keys are frequently needed

Question 23

What is Lazy Loading / Cache-Aside / Lazy population?

Answer 23

In the case of a cache miss, read from DB and write the data to cache (can be slow, data can get stale)

Question 24

What is write through?

Answer 24

When application writes to DB, also write to the cache (data in cache never stale, but a lot of the data will never be read)

Question 25

Cache evictions 3 ways

Answer 25

- delete item in cache - item is evicted because memory is full or not recently used - you set time to live (TTL)