Databases Flashcards

1
Q

Standby Instance

A

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

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2
Q

RDS Multi-AZ Failover

A
  • -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.
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3
Q

RDS Backups

A
  • -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.
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4
Q

RDS Read Replicas

A
  • -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.
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5
Q

Benefits of using Read Replicas

A
    • 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.
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6
Q

when to use read replicas

A

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.

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7
Q

DynamoDB use cases

A

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

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8
Q

DynamoDB

A

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

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9
Q

ElastiCache

A
  • 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.
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10
Q

Available engines to power ElastiCache

A

Memcached and Redis

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11
Q

Redshifts

A
  • 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
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