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CLF-C02 · Domain 3: Cloud Technology and Services · 34% of the exam

Task 3.4: Identify AWS database services.

Relational, key-value and in-memory databases, managed versus self-hosted on EC2, and the tools that migrate a database to AWS.

Study it

  • Databases: RDS, Aurora, DynamoDB, ElastiCache, DMS and SCT

    Partly covered by: RDS vs DynamoDB

Sample questions

Try each one before opening the answer. Every option is explained, with the AWS documentation page that proves it.

Question 1 · choose 1

A mobile game stores player profiles that are always read and written by player ID. Responses must stay in single-digit milliseconds as the player base grows from thousands to millions, and the team wants no servers to provision or patch. Which database fits?

  1. AAmazon DynamoDB
  2. BAmazon RDS for MySQL
  3. CAmazon Redshift
  4. DA database the team installs on Amazon EC2
Show the answer and why

  • AAmazon DynamoDB

    Correct

    DynamoDB is a serverless NoSQL database with key-value access and single-digit millisecond performance at any scale, with no servers to provision or patch.

  • BAmazon RDS for MySQL

    Incorrect

    RDS is the managed relational choice, but it runs on DB instances whose class you pick and resize as you grow; key lookups at any scale with no servers describe DynamoDB.

  • CAmazon Redshift

    Incorrect

    Redshift is a petabyte-scale data warehouse for analytical SQL queries, not a store for per-player reads and writes.

  • DA database the team installs on Amazon EC2

    Incorrect

    On EC2 the team manages the guest operating system and the database software, including patching — the work it wants to avoid.

Access by key, steady low latency at any scale and zero servers to run is the case DynamoDB is built for.

AWS documentation

Lesson: RDS vs DynamoDBTask 3.4Report a problem with this question

Question 2 · choose 1

An online shop's application reads the same product catalog from its relational database thousands of times a second. The team wants to put an in-memory cache in front of the database to take load off it and speed up responses. Which service should it use?

  1. AAmazon ElastiCache
  2. BAmazon Redshift
  3. CAWS Database Migration Service (AWS DMS)
  4. DAmazon S3 Glacier Instant Retrieval
Show the answer and why

  • AAmazon ElastiCache

    Correct

    ElastiCache sets up, manages and scales a distributed in-memory data store or cache, a high-performance way to serve repeated reads without going to the database.

  • BAmazon Redshift

    Incorrect

    Redshift is a petabyte-scale data warehouse for analytical queries, not a cache for an application's repeated reads.

  • CAWS Database Migration Service (AWS DMS)

    Incorrect

    DMS migrates and replicates data between data stores. It does not serve reads to an application.

  • DAmazon S3 Glacier Instant Retrieval

    Incorrect

    This is a storage class for long-lived archive data accessed about once a quarter, not an in-memory cache.

When the same data is read over and over, keep a copy in memory. ElastiCache is AWS's managed in-memory cache and data store.

AWS documentation

Lesson: RDS vs DynamoDBTask 3.4Report a problem with this question

Question 3 · choose 2

A company is moving an on-premises Oracle database to Amazon Aurora PostgreSQL-Compatible Edition. The schema must be converted to the new engine, and the Oracle database must stay in use, with ongoing changes copied across until the cutover. Which AWS tools fit these two needs? (Choose TWO.)

  1. AAWS DataSync
  2. BAWS Schema Conversion Tool (AWS SCT)
  3. CAWS Database Migration Service (AWS DMS)
  4. DAWS Storage Gateway
  5. EAWS Backup
Show the answer and why

  • AAWS DataSync

    Incorrect

    DataSync moves files and objects between storage systems. It does not convert a database schema or replicate database changes.

  • BAWS Schema Conversion Tool (AWS SCT)

    Correct

    AWS SCT converts an existing database schema from one engine to another, such as Oracle to Aurora PostgreSQL.

  • CAWS Database Migration Service (AWS DMS)

    Correct

    AWS DMS migrates the data and can replicate ongoing changes to keep the source and target in sync until cutover.

  • DAWS Storage Gateway

    Incorrect

    Storage Gateway gives on-premises applications access to cloud storage. It does not migrate a database between engines.

  • EAWS Backup

    Incorrect

    AWS Backup centralizes and automates backups of AWS resources. A backup cannot change the database engine.

A change of engine needs two steps: convert the schema (AWS SCT, or DMS Schema Conversion), then move the data and keep it in sync (AWS DMS).

AWS documentation

Task 3.4Report a problem with this question

Question 4 · choose 1

A company wants a fully managed relational database that is compatible with MySQL and PostgreSQL, so its existing code and tools keep working, and whose storage grows automatically as data is added. Which service fits?

  1. AAmazon DynamoDB
  2. BAmazon Redshift
  3. CAmazon Aurora
  4. DAmazon ElastiCache
Show the answer and why

  • AAmazon DynamoDB

    Incorrect

    DynamoDB is a NoSQL key-value and document database, not a MySQL- or PostgreSQL-compatible relational engine.

  • BAmazon Redshift

    Incorrect

    Redshift is a petabyte-scale data warehouse for analytics, not an application's relational database.

  • CAmazon Aurora

    Correct

    Aurora is a fully managed relational database engine compatible with MySQL and PostgreSQL, and its underlying storage grows automatically as needed.

  • DAmazon ElastiCache

    Incorrect

    ElastiCache is an in-memory data store and cache, not a relational database of record.

Relational on AWS means Amazon RDS, and Aurora is the cloud-built engine inside RDS for MySQL- and PostgreSQL-compatible workloads.

AWS documentation

Lesson: RDS vs DynamoDBTask 3.4Report a problem with this question

Question 5 · choose 2

A team needs a relational database with SQL tables, joins and transactions for its order system. Which of the following are AWS relational database services? (Choose TWO.)

  1. AAmazon RDS
  2. BAmazon DynamoDB
  3. CAmazon Aurora
  4. DAmazon ElastiCache
  5. EAmazon Neptune
Show the answer and why

  • AAmazon RDS

    Correct

    Amazon RDS sets up, operates and scales relational databases with engines such as MySQL, PostgreSQL, Oracle and SQL Server.

  • BAmazon DynamoDB

    Incorrect

    DynamoDB is a NoSQL database with key-value and document models; it does not support JOIN operations.

  • CAmazon Aurora

    Correct

    Aurora is a fully managed relational database engine compatible with MySQL and PostgreSQL, part of Amazon RDS.

  • DAmazon ElastiCache

    Incorrect

    ElastiCache is an in-memory data store and cache.

  • EAmazon Neptune

    Incorrect

    Neptune is a graph database service for highly connected data, not a relational database.

Relational: RDS and Aurora. Key-value and document: DynamoDB. In-memory: ElastiCache. Graph: Neptune.

AWS documentation

Lesson: RDS vs DynamoDBTask 3.4Report a problem with this question

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