DBS-C01 Workload-Specific Database Design Practice Question
Network Topology
A company is running an Amazon RDS for MySQL instance as shown in the exhibit. The application is experiencing high write latency. The instance has a high number of write operations and the storage queue depth is consistently above 100. Which change would most effectively reduce write latency?
⚠ Common exam trap
It's easy for candidates to confuse Multi-AZ replication as a way to distribute write load, but in reality, Multi-AZ only handles failover and read replicas for reads, not writes, and increasing storage or instance size without addressing the IOPS bottleneck will not resolve high queue depth.
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
✓
Modify the storage type to Provisioned IOPS (io1) with 3000 IOPS.
The instance is experiencing high write latency with a consistently high storage queue depth (above 100), which indicates that the current storage (likely gp2 or magnetic) cannot keep up with the write IOPS demand. Provisioned IOPS (io1) with 3000 IOPS guarantees a dedicated level of IOPS, reducing queue depth and write latency by ensuring the storage subsystem can handle the write workload without throttling.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Modify the storage type to Provisioned IOPS (io1) with 3000 IOPS.
Why this is correct
Provisioned IOPS provides consistent, low-latency performance.
- ✗
Change the instance class to db.m5.xlarge.
Why it's wrong here
Instance class is not the bottleneck; storage IOPS is.
- ✗
Enable Multi-AZ to offload writes to a standby.
Why it's wrong here
Multi-AZ is for availability, writes go to primary only.
- ✗
Increase the allocated storage to 200 GB.
Why it's wrong here
Increasing gp2 storage increases baseline IOPS, but not as effectively as io1.
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