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AWS Professional > 07 Databases > Flashcards

07 Databases Flashcards

1
Q

Describe the purpose of Relational Database Service (RDS).

A

Relational Database Service (RDS) provisions and manages database servers, allowing each server to run one or many databases.

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2
Q

List the supported database engines for RDS.

A

The supported engines for RDS include MySQL, MariaDB, PostgreSQL, Oracle, and Microsoft SQL Server.

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3
Q

How is database storage managed in RDS?

A

Database storage in RDS is managed using EBS, with each instance having its own dedicated volume.

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4
Q

Explain the concept of Multi-AZ in RDS.

A

Multi-AZ in RDS provides high availability by using a primary instance in one Availability Zone (AZ) that synchronously replicates to a stand-by instance in another AZ.

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5
Q

What happens during a failover in a Multi-AZ instance?

A

During a failover in a Multi-AZ instance, access to the database is redirected to the current primary instance, but there will be downtime while DNS records update and reach TTL.

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6
Q

Define the structure of a Multi-AZ Cluster in RDS.

A

A Multi-AZ Cluster in RDS consists of one writer instance that synchronously replicates to two reader instances in other AZs, allowing the reader instances to be used for read operations.

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7
Q

How are writes considered replicated in a Multi-AZ Cluster?

A

Writes in a Multi-AZ Cluster are considered replicated when they have been replicated to at least one reader instance.

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8
Q

What are the three types of endpoints used in a Multi-AZ Cluster?

A

The three types of endpoints are: the cluster endpoint (points to the writer), the reader endpoint (points to any available reader), and individual instance endpoints (not recommended for direct use).

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9
Q

Describe the backup process in RDS.

A

Backups in RDS capture the state of the database server and are stored in S3, with automated backups made on a schedule and snapshots created ad-hoc.

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10
Q

What is the difference between automated backups and snapshots in RDS?

A

Automated backups are scheduled and retained for up to 35 days, while snapshots are ad-hoc and retained until deleted.

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11
Q

How does Multi-AZ impact the backup process?

A

If Multi-AZ is enabled, backups are made from the stand-by instance to reduce performance impact on the primary instance.

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12
Q

Explain the frequency of transaction log captures in RDS.

A

Transaction logs in RDS are captured every 5 minutes to allow restoration to a precise time frame.

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13
Q

What is cross-region replication in RDS?

A

Cross-region replication in RDS can be enabled for backups and snapshots, allowing data to be replicated across different geographic regions.

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14
Q

How are restores performed in RDS?

A

Restores in RDS are performed by creating a new RDS instance based on the backup or snapshot.

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15
Q

Describe the purpose of promoting a read replica in RDS.

A

Promoting a read replica allows for a near-zero Recovery Time Objective (RTO), making it particularly helpful for cross-region disaster recovery.

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16
Q

How does RDS Proxy improve database performance?

A

RDS Proxy establishes long-term connections with clients and maintains a pool of connections to the database, which improves performance and helps avoid exhausting connections.

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17
Q

Define the role of IAM authentication in RDS.

A

IAM authentication is performed by calling GenerateDbAuthToken and mapping the IAM identity to a local RDS user for authorization.

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18
Q

Explain the significance of shared storage in Aurora.

A

Aurora uses shared storage instead of an EBS volume for each server, allowing data to be stored across three Availability Zones (AZs) for redundancy and enabling rapid provisioning of replicas.

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19
Q

What is the function of the cluster endpoint in an Aurora database?

A

The cluster endpoint is used for write and management operations within an Aurora database cluster.

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20
Q

How does Backtrack feature work in Aurora?

A

Backtrack allows in-place rewinds of the database without the need to restore to a brand new database.

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21
Q

Describe the cloning process in Aurora.

A

The Clone feature creates a new database that references another database and only stores changes, utilizing a copy-on-write mechanism.

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22
Q

What is the maximum number of read replicas that a write instance can have in RDS?

A

Each write instance can have a maximum of 5 read replicas.

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23
Q

How does RDS Custom differ from standard RDS?

A

RDS Custom allows for customization of the underlying operating system and database engine, enabling administrators to manually apply patches using SSH, SSM, or RDP.

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24
Q

Explain the concept of multi-master writes in Aurora.

A

Multi-master writes in Aurora allow multiple instances to write data simultaneously, requiring a quorum of replicas to agree upon receiving a write request.

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25
Q

What is the purpose of EBS volume encryption in RDS?

A

EBS volumes used by RDS can be encrypted using KMS to enhance data security, with some database engines natively supporting encryption.

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26
Q

Describe the replication method used by Read Replicas in RDS.

A

Read Replicas use asynchronous replication and can be created in other regions to enhance data availability.

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27
Q

What is the role of the reader endpoint in an Aurora cluster?

A

The reader endpoint in an Aurora cluster load balances read requests across the replicas.

28
Q

How does RDS Proxy ensure low-latency connections?

A

RDS Proxy is recommended for low-latency connections, such as those required by Lambda functions, by maintaining active connections to the database.

29
Q

What happens to the cost structure in recent versions of Aurora?

A

Recent versions of Aurora have shifted from a high water mark cost structure to a more scalable model.

30
Q

How many copies of data does Aurora store across multiple AZs?

A

Aurora stores 6 copies of the data across multiple Availability Zones (AZs) for redundancy.

31
Q

Describe how Aurora Serverless scales databases.

A

Aurora Serverless scales databases without directly provisioning instances, based on Aurora Capacity Units (ACUs).

32
Q

Explain the implications of scaling down to 0 in Aurora Serverless.

A

Scaling down to 0 will pause the database, which incurs an overhead cost.

33
Q

Define RDS Proxy in the context of Aurora Serverless.

A

Database connections in Aurora Serverless are managed through RDS Proxy.

34
Q

How does DynamoDB ensure high availability?

A

DynamoDB is a highly-available managed key-value NoSQL database.

35
Q

Describe the structure of tables in DynamoDB.

A

Tables in DynamoDB are a grouping of items that use the same primary key.

36
Q

What are the two types of primary keys in DynamoDB?

A

The two types of primary keys in DynamoDB are Simple (just the partition key) and Composite (a partition key and a sort key).

37
Q

Explain the uniqueness requirement of primary keys in DynamoDB.

A

The primary key must be unique in the table, whether it is simple or composite.

38
Q

How large can items be in DynamoDB?

A

Items in DynamoDB can be up to 400 KB each.

39
Q

Define the Provisioned capacity mode in DynamoDB.

A

Provisioned capacity mode allows setting a specific number of read capacity units (RCUs) and write capacity units (WCUs) on a per-table basis.

40
Q

What is the function of one RCU in DynamoDB?

A

One RCU performs strongly consistent reads up to 4 KB per second, which can be across multiple items in a single operation.

41
Q

Describe the function of one WCU in DynamoDB.

A

One WCU allows writing up to 1 KB per second, which can also be across multiple items in a single operation.

42
Q

Explain the concept of burst pool in DynamoDB.

A

Every table in DynamoDB has a burst pool of 300 seconds worth of RCUs and WCUs.

43
Q

What is the On-demand capacity mode in DynamoDB?

A

On-demand capacity mode allows DynamoDB to scale capacity automatically without any overhead except for storage.

44
Q

Define On-demand backups in DynamoDB.

A

On-demand backups are a point-in-time copy of the table, taken manually and stored until deleted, allowing restoration to the same or another region.

45
Q

What is Point-in-time Recovery in DynamoDB?

A

Point-in-time Recovery collects all changes made in a rolling 35-day window, allowing restoration to any point with one second granularity, and must be enabled on a per-table basis.

46
Q

Describe the Query operation in DynamoDB.

A

The Query operation retrieves data based on a single value of the primary key, and optionally a single value for the sort key or a rate.

47
Q

How does the Scan operation work in DynamoDB?

A

The Scan operation searches across the entire table and provides more flexible filtering options.

48
Q

Describe the consistency models available in DynamoDB.

A

DynamoDB offers eventually consistent reads by default, which are less expensive, allowing one RCU to read two items. Strong consistency can be selected when required.

49
Q

Define Local Secondary Index (LSI) in DynamoDB.

A

An LSI allows a different sort key with the same partition key and must be created when the table is set up. Up to 5 LSIs can be created, sharing capacity with the main table.

50
Q

How does a Global Secondary Index (GSI) differ from a Local Secondary Index (LSI)?

A

A GSI allows a different sort key and primary key, can be created at any time, and supports up to 20 per table. It uses separate RCUs and WCUs from the main table.

51
Q

Explain the purpose of Streams in DynamoDB.

A

Streams are time-ordered lists of changes to items in a table, retained for 24 hours, and can trigger Lambda functions for specific changes.

52
Q

What is DynamoDB Accelerator (DAX) and its primary benefit?

A

DAX is an in-memory cache that supports read-through and write-through caching, primarily benefiting read operations.

53
Q

Describe the functionality of Global Tables in DynamoDB.

A

Global Tables provide multi-master cross-region replication, allowing reads and writes in any region with conflict resolution using ‘last writer wins’.

54
Q

How does Time-to-Live (TTL) work in DynamoDB?

A

TTL can be applied to items to cause them to expire when the current epoch exceeds a specified attribute, with expired items deleted by a sweeper process.

55
Q

Define the role of Athena in relation to data stored in S3.

A

Athena performs ad-hoc queries on structured or unstructured data stored in S3 and CloudTrail, enabling flexible data analysis.

56
Q

Describe the types of data formats supported by Athena.

A

Athena supports various data formats including XML, JSON, and Parquet.

57
Q

Define the requirement for querying in Athena.

A

The schema must be defined within Athena before querying.

58
Q

How do federated queries enhance Athena’s capabilities?

A

Federated queries allow Athena to query non-S3 datasources using a data connector.

59
Q

What is Neptune and what are its features?

A

Neptune is a managed graph database that has features similar to RDS, such as MultiAZ and Point-In-Time Recovery (PITR).

60
Q

Explain the purpose of Quantum Ledger Database (QLDB).

A

QLDB provides a cryptographically-verifiable database with guaranteed transaction logging using blockchain technology.

61
Q

Describe ElastiCache and its use cases.

A

ElastiCache is a managed in-memory cache recommended for read-heavy workloads where low-latency is required.

62
Q

What engines does ElastiCache support?

A

ElastiCache supports the Redis, Memcached, and Valkey engines.

63
Q

How does Redis ensure high availability?

A

Redis supports Multi-AZ replication for high availability.

64
Q

Compare the performance characteristics of Redis and Memcached.

A

Redis supports advanced data structures and Multi-AZ replication, while Memcached can be more performant due to its support for multi-threading.

65
Q

What is a key difference between ElastiCache and DAX?

A

Unlike DAX, ElastiCache requires changes to the application.

AWS Professional (10 decks)

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