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AWS Certified Data Engineer > Database > Flashcards

Database Flashcards

1
Q

Define DynamoDB.

DynamoDB Flashcards: Core Concepts

A

A fully managed, serverless, key-value NoSQL database offering high performance and scalability for any scale.

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2
Q

What are the core components of DynamoDB?

A

Tables, Items, Attributes, and Primary Keys (Partition Key or Partition Key + Sort Key)

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3
Q

Explain the function of a DynamoDB Partition Key.

A

Distributes data across partitions, ensuring even distribution and efficient data access. Must be unique for each item.

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4
Q

What role does a Sort Key play?

A

Organizes data within a partition, enabling range queries and sorting within a partition.

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5
Q

What data types does DynamoDB support?

A

Scalar (String, Number, Binary, Boolean, Null), Document (List, Map), and Set types (String Set, Number Set, Binary Set).

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6
Q

Differentiate between Provisioned and On-Demand capacity modes.

A
  • Provisioned: User defines read/write capacity units (RCUs/WCUs). Offers cost predictability.
  • On-Demand: DynamoDB automatically scales capacity. Ideal for unpredictable workloads.
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7
Q

What are the benefits of DynamoDB Streams?

A

Capture item-level modifications (create, update, delete) for real-time reactions, analytics, cross-region replication, and other event-driven architectures.

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8
Q

How does DynamoDB Time To Live (TTL) work?

A

Automatically deletes items after a defined time period based on a “Number” attribute containing the Unix Epoch timestamp.

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9
Q

How do you write data to DynamoDB?

A

Using PutItem (create or replace), UpdateItem (modify existing), and BatchWriteItem (for multiple items).

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10
Q

Explain Conditional Writes in DynamoDB.

A

Allow write operations only if specific conditions are met, preventing unintended overwrites and supporting atomic operations.

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11
Q

What are the primary ways to read data from DynamoDB?

A

GetItem (retrieve by primary key), Query (retrieve items based on partition key and optional sort key conditions), Scan (scan the entire table with optional filters).

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12
Q

What is the purpose of BatchGetItem?

A

Retrieves multiple items from one or more tables in a single API call, improving efficiency.

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13
Q

Compare Eventually Consistent Reads and Strongly Consistent Reads.

A
  • Eventually Consistent: May return stale data due to replication lag. Higher performance, lower cost.
  • Strongly Consistent: Guarantees the latest data. Consumes more RCUs.
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14
Q

How do you delete data in DynamoDB?

A

DeleteItem (delete a single item), BatchWriteItem (delete multiple items), DeleteTable (delete the entire table).

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15
Q

What are Local Secondary Indexes (LSIs)?

A

Alternative sort keys for a table, using the same partition key as the base table. Defined at table creation.

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16
Q

What are Global Secondary Indexes (GSIs)?

A

Indexes with a different partition key and/or sort key from the base table. Can be created after table creation.

17
Q

What is the impact of throttling on GSIs?

A

If writes to a GSI are throttled, writes to the main table are also affected, even if the main table has sufficient WCUs.

18
Q

How does DynamoDB Accelerator (DAX) improve performance?

A

Provides an in-memory cache for DynamoDB, significantly reducing read latency, especially for frequently accessed data (“hot keys”).

19
Q

What is PartiQL?

A

A SQL-compatible query language for DynamoDB, enabling familiar SQL-like syntax for data operations.

20
Q

Describe the Large Object pattern in DynamoDB.

A

For storing large items (> 400KB), store the data in S3 and metadata in DynamoDB.

21
Q

How can you control access to DynamoDB at a granular level?

A

Use IAM roles with conditions, specifying LeadingKeys (row-level access) and Attributes (attribute-level access).

22
Q

What are DynamoDB Global Tables?

A

Multi-region, multi-active tables that replicate data across AWS regions for high availability and low latency globally.

23
Q

What is Amazon RDS?

A

A managed relational database service supporting popular engines like MySQL, PostgreSQL, Oracle, SQL Server, etc.

24
Q

What are the key benefits of using RDS?

A

Easy setup, operation, and scaling; automated backups; high availability; security features.

25
Q

What is Amazon Aurora?

A

A MySQL and PostgreSQL-compatible relational database designed for the cloud, offering high performance, scalability, and cost-effectiveness.

26
Q

Explain the ACID properties in the context of RDS.

A

Atomicity, Consistency, Isolation, and Durability – guarantees for reliable transaction processing.

27
Q

What are the different types of locks in RDS?

A

Shared locks (allow concurrent reads) and Exclusive locks (prevent all other operations).

28
Q

List some RDS best practices.

A

Monitor with CloudWatch, perform regular backups, test failover, optimize queries with indexes, and use read replicas.

29
Q

How can you optimize query performance in RDS?

A

Use indexes, analyze query plans, avoid full table scans, and use database-specific tuning techniques.

30
Q

What is Amazon DocumentDB?

A

A MongoDB-compatible, document database service offering high scalability and availability.

31
Q

What is Amazon MemoryDB for Redis?

A

A Redis-compatible, in-memory database with data durability, providing ultra-fast performance for caching and real-time applications.

32
Q

What is Amazon Keyspaces (for Apache Cassandra)?

A

A managed service for running Apache Cassandra, a highly scalable and available NoSQL database.

33
Q

What is Amazon Neptune?

A

A fully managed graph database service for applications dealing with highly connected datasets, like social networks and knowledge graphs.

34
Q

What is Amazon Timestream?

A

A serverless time series database optimized for storing and analyzing time-stamped data, commonly used for IoT and operational analytics.

AWS Certified Data Engineer (14 decks)

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