AWS Database Specialty - DBS-C01

1. 1.An application stores highly connected data and must answer queries such as which accounts are within four relationship hops of a flagged entity, with millisecond latency. Which database should be selected?

   • AAmazon NeptuneCorrect answer
   • BAmazon RDS for PostgreSQL with recursive CTEs
   • CAmazon DynamoDB with a composite sort key
   • DAmazon Redshift with materialized views

   Why

   Amazon Neptune is a purpose-built graph database that traverses relationships natively and answers multi-hop queries efficiently using Gremlin or openCypher. A relational engine would require recursive joins that degrade sharply with depth, DynamoDB has no traversal primitive, and Redshift is a columnar analytical warehouse.

2. 2.A regulated application must maintain a cryptographically verifiable, immutable history of every change to financial records, provable to an auditor. Which database fits?

   • AAmazon QLDBCorrect answer
   • BAmazon RDS with audit triggers writing to a history table
   • CAmazon DynamoDB with Streams enabled
   • DAmazon S3 with Object Lock in compliance mode

   Why

   Amazon QLDB provides an immutable, append-only journal with a cryptographic digest that lets an auditor verify that no record was altered or deleted. A relational database with triggers can log changes but a privileged user could modify the log, DynamoDB Streams captures changes without an immutable verifiable journal, and S3 Object Lock protects objects rather than providing a transactional ledger.

3. 3.An IoT platform ingests millions of timestamped measurements per second and queries recent time windows, with older data automatically moved to cheaper storage. Which database is purpose-built?

   • AAmazon TimestreamCorrect answer
   • BAmazon DynamoDB with a TTL attribute
   • CAmazon RDS for MySQL with partitioned tables
   • DAmazon Redshift with a sort key on the timestamp

   Why

   Amazon Timestream is a time series database that ingests high-volume timestamped data, tiers recent data in memory and older data to magnetic storage automatically, and provides time series analytic functions. DynamoDB would require building the tiering with TTL and a second store, RDS cannot sustain that ingest rate, and Redshift targets batch analytics rather than continuous ingestion.

4. 4.An Aurora MySQL cluster must promote a specific replica first during failover, and a second replica only if the first is unavailable. What should be configured?

   • AFailover priority tiers on the Aurora ReplicasCorrect answer
   • BA larger instance class on the preferred replica
   • CThe cluster reader endpoint
   • DMulti-AZ enabled on the cluster

   Why

   Set the failover priority tier on each Aurora Replica, where tier-0 is promoted before tier-1 and Aurora selects the largest replica among equal tiers. A larger instance class influences selection only among equal tiers, a read-only endpoint distributes reads, and Multi-AZ is the underlying property rather than the promotion order control.

5. 5.A design must give an application sub-millisecond reads of DynamoDB items that are read repeatedly, without changing the application's DynamoDB API calls. Which service should be added?

   • AAmazon DynamoDB AcceleratorCorrect answer
   • BAmazon ElastiCache for Redis in front of the table
   • CAn additional global secondary index
   • DHigher provisioned read capacity on the table

   Why

   Add Amazon DynamoDB Accelerator, an in-memory cache that is API-compatible with DynamoDB so the application keeps its existing calls while cached reads return in microseconds. ElastiCache would require the application to manage cache reads and writes explicitly, a global secondary index changes access patterns rather than latency, and increasing provisioned capacity does not reduce per-read latency.

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