Databases

Question 1

Standby Instance

Answer 1

Multi-AZ Failover. should be in the same region.

Question 2

RDS Multi-AZ Failover

Answer 2

• -automatically switch the CNAME DNS record from the primary instance to the stand-by instance.
• -RDS BACKUPS ARE TAKEN AGAINST THE STAND-BY INSTANCE TO REDUCE I/O FREEZES AND SLOW DOWN IF MULTI-AZ IS ENABLED.
• -In order for multi-az to work, your primary database instance must be launched into a “subnet group”.
• • an RDS instance must be launched into a subnet(inside a VPC), just like an EC2 instance so the same security/connectivity rules, and highly available/fault tolerant concepts apply.

Question 3

RDS Backups

Answer 3

• -automated point-in-time backups
• -automated backups are deleted once the database instance is deleted and connot be recovered’.
• -backups on database engines only work correctly when the database engine is “transactional”, but do currently work for all supported database types.
• -MYSQL requires innoDB for reliable backups.

Question 4

RDS Read Replicas

Answer 4

• -asynchronous copies of the primary database taht are used for read only purposes(only allow “read connections”).
• -when you write new data to the primary database, AWS copies it for you to the read replica.
• -can create and have multiple read replicas for a primary database.
• • can be created from other read replicas so no performance hit on the primary database.
• • can monitor replication lag using cloudwatch.
• • MySQL, MariaDB, PostgreSQL, and Aurora currently support read replicas.

Question 5

Benefits of using Read Replicas

Answer 5

• • traffic redirected from the primary database to the read replica so improove performance on the primary database
• • elasticity in RDS (you can add more read replicas as demand increases.
• • can promote a read replica to a primary instance
• • MYSQL – replicate for improting/exporting data to RDS; can replicate across regions.

Question 6

when to use read replicas

Answer 6

High volume, non-cached database read triffic(elasticity)
Running business function such as data warehousing.
importing/exporting data into RDS.
rebuilding indexes: ability to promote a read replica to a primary instance.

Question 7

DynamoDB use cases

Answer 7

IOT(Storing meta data);
Gaming(storing session information, leaderboards)
Mobile(storing user profile, personalization).

Question 8

DynamoDB

Answer 8

easily integrates with other AWS services, such as Elastic MapReduce – can easily move data to a hadoop cluster in Elastic MapReduce.

Question 9

ElastiCache

Answer 9

• fully managed, in-memory cache Engine
• used to improve database performance by caching results of queries that are made to a database.
• great for large, high-performance or high-taxing queries – can store them inside of a cache(Elastic Cache Cluster) that can be accessed later(instead of repeat request continually hitting the primary database).
• reduce load on the database which increases performance.
• ElastiCache allows for managing web sessions, and also caching dynamic generated data.

Question 10

Available engines to power ElastiCache

Answer 10

Memcached and Redis

Question 11

Redshifts

Answer 11

• a petabyte-scale data warehousing service
• fully managed and scalable.
• for big-data analytics and can integrate with most popular business tools:
  Jaspersoft;
  Microstratey
  Pentaho
  Tableau
  Business Objects
  Congnos