DBS-C01 Management and Operations Practice Question
A company runs a critical application on Amazon RDS for PostgreSQL with Multi-AZ. The database has a large table (over 500 GB) that is frequently updated. The operations team notices that the primary instance's CPU usage is consistently above 90%, and the replica lag between the primary and standby is increasing during peak hours. The application can tolerate a few seconds of downtime. The team needs to reduce CPU load and improve write performance without changing the application code. Which action should be taken?
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
✓
Upgrade the DB instance class to a larger size with more vCPUs.
Upgrading to a larger DB instance class provides additional vCPUs, reducing CPU utilization and alleviating replication lag. Option B is wrong: increasing the backup retention period does not reduce I/O during backups; it only keeps backups longer and does not address CPU or write performance. Option C is wrong: Multi-AZ RDS for PostgreSQL uses synchronous replication; switching to asynchronous replication is not possible without compromising durability, and it would not reduce CPU load on the primary. Option D is wrong: creating a read replica offloads read queries, but it does not reduce write load or CPU usage from writes on the primary instance; replication lag may persist or increase.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Upgrade the DB instance class to a larger size with more vCPUs.
Why this is correct
More CPU capacity reduces the load on the primary and helps keep up with replication.
- ✗
Increase the backup retention period to reduce I/O during backups.
Why it's wrong here
Backup retention does not significantly affect CPU usage or replication lag.
- ✗
Modify the DB instance to use asynchronous replication instead of synchronous.
Why it's wrong here
Multi-AZ uses synchronous replication; switching to async is not supported for Multi-AZ and would risk data loss.
- ✗
Create a read replica in the same region and offload read queries to it.
Why it's wrong here
Read replicas reduce read load, but the issue is write-related CPU usage and replication lag.
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