Databases Flashcards
Does Multi-AZ RDS allow to create instances in different regions?
No, only in different AZs of the same region
How would you store session data?
With ElastiCache
In alternative, it can be done by activating sticky session in ELB, but this might cause unbalanced traffic across instances
Can you combine Read Replicas and Multi-AZ in a RDS instance?
Yes
In a Multi-AZ RDS, what happens if the primary instance fails?
A secondary replica instance is elected as a primary source of replication
Can you use RDS Cross Region for write failover?
No, Cross Region is used to create Read Replicas across multiple regions. Use Multi-AZ instead
What does RDS use for database and log storage?
EBS Volume
You try to connect to your RDS instance and you receive an “Error setting/closing connection: Connection refused”. What is most likely the cause of the connection failure?
Incorrect DNS name or endpoint was used to connect to the RDS instance
You have a RDS instance. Which services are you going to pay for it between:
- Data transfer
- RDS CloudWatch metrics
- Data storage
- I/O requests per month
Everything excepts CloudWatch metrics
How many types of secondary indexes does DynamoDB support?
2, Local secondary index and Global secondary index
Does Aurora support schema changes?
Yes
What type of replication is supported by Multi-AZ RDS instances?
Synchronous replication
Does Aurora support cross-region replication?
Only for MySQL, not for PostgreSQL
What is the difference in Aurora between cross-region logical replication and cross-region physical replication?
Physical replication can only replicate to one secondary region, logical replication can replicate to multiple regions
Can you assign network capacity to RDS instances?
Yes
What type of replication are RDS Multi-AZ and Read Replicas?
Multi-AZ is syncronous
Read Replicas is asynchronouse and can be within AZ, Cross-AZ, Cross-Region
Can you enable storage auto scaling for RDS?
Yes, if you enable it these factors apply:
Free available space is less than 10 percent of the allocated storage.
The low-storage condition lasts at least five minutes.
At least six hours have passed since the last storage modification.
The maximum storage threshold is the limit that you set for autoscaling the DB instance.
Can you set standby instances for Aurora Multi-AZ?
No, only for RDS Multi-AZ
What traffic charges involve data replication with RDS?
There are changes only between replication through different regions. No traffic charges for replication across AZs of the same region
What’s the difference between a RDS with Multi-AZ or RDS with standby read replicas?
Read replicas do not support automatic failover, promotion to primary instance is manual.
Multi-AZ failover is automatic
What’s the difference between RDS Multi-AZ and Aurora Multi-AZ?
RDS: failover is done with standby instance
Aurora: failover is done with read replica (no standby instances)
https://aws.amazon.com/rds/features/read-replicas/
What’s the maximum retention period for automated backups in RDS?
35 days. To increase the retention, you need to create a backup plan with AWS Backup
How can you change the instance class of a running Aurora db to serverless?
The only way to do that without down time is to use AWS Database Migration Service with ongoing replication
Other methods (with downtime) are:
Take a snapshot and use that to create a new Aurora instance
Add an Aurora replica to the cluster with serverless type. Failover to the read replica and promote it to primary
What happens if you have a serverless Aurora DB and it fails?
Aurora tries to create a new database instance in a new AZ
What happens if you have a single instance Aurora DB (not serverless) and it fails?
Aurora tries to create a new database instance in the same AZ
Are there data transfer charges for replicating RDS across read replicas in the same region?
No, charges apply only for replicating to a different region
