DBS-C01 Management and Operations Practice Question
A logistics company operates a fleet tracking system using Amazon DocumentDB (with MongoDB compatibility). The database stores location updates from thousands of vehicles every second. The collection has a compound index on (vehicle_id, timestamp). Recently, the company noticed that write latency has increased, and the primary instance's CPU is consistently above 80%. The storage is gp2, and the instance is a db.r5.large. The operations team suspects that index maintenance is causing high CPU. The database administrator needs to reduce write latency without sacrificing query performance for real-time location queries. What should the administrator do?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Shard the collection using a hash-based shard key on vehicle_id to distribute write load.
Sharding the collection using a hash-based shard key on vehicle_id distributes writes evenly and reduces index maintenance overhead. Option A is wrong because removing the compound index harms query performance for real-time location queries. Option B is wrong because upgrading to a larger instance class adds CPU but does not address the root cause of index maintenance overhead. Option C is wrong because disabling journaling reduces durability, not index maintenance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Remove the compound index and rely on the default _id index for queries.
Why it's wrong here
Removing the compound index would harm query performance, especially for the real-time location queries that rely on filtering by vehicle_id and timestamp.
- ✗
Upgrade to a larger instance class, such as db.r5.xlarge, to provide more CPU and memory.
Why it's wrong here
Increasing instance size adds CPU but does not address the root cause of index maintenance overhead.
- ✗
Disable journaling to reduce write I/O.
Why it's wrong here
Disabling journaling reduces write durability, not index maintenance overhead. It does not address the CPU issue and risks data loss.
- ✓
Shard the collection using a hash-based shard key on vehicle_id to distribute write load.
Why this is correct
Sharding the collection using a hash-based shard key on vehicle_id distributes writes evenly and reduces index maintenance overhead.
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Written by Johnson Ajibi, MSc IT Security
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This DBS-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DBS-C01 exam.