CV0-004 Troubleshooting Practice Question
During a disaster recovery test, a cloud administrator discovers that the standby database in a different region is not synchronized with the primary. The primary database uses asynchronous replication. What is the MOST likely reason for the sync failure?
⚠ Common exam trap
CV0-004 often tests the distinction between synchronous and asynchronous replication — candidates pick 'firewall blocking port' because it sounds like a concrete failure, but a blocked port would cause total replication failure, not a lag/sync gap, which is the hallmark of async replication under latency.
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
✓
Network latency causing replication lag
Asynchronous replication does not wait for the standby to acknowledge each write, so the standby can lag behind the primary. Cross-region replication is especially sensitive to network latency, which directly increases replication lag and can cause the standby to fall out of sync during a DR test. This is the most likely cause given the asynchronous, cross-region setup.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
License expiration on the standby database
Why it's wrong here
Licence expiry would halt the standby engine entirely, not leave it running yet lagging behind the primary. Licensing is the correct focus when a database refuses to start or features are disabled after a subscription lapses, but it cannot explain a standby that is up yet asynchronously behind.
- ✓
Network latency causing replication lag
Why this is correct
Asynchronous replication commits on the primary without waiting for the standby, so inter-region network latency directly manifests as replication lag. Sustained latency prevents the standby from ever catching up, which is the expected failure mode for cross-region async setups.
- ✗
Firewall rules blocking port 3306 between regions
Why it's wrong here
Blocking port 3306 would sever the replication connection completely, producing connection errors rather than a standby that is merely behind. Firewall rules are the correct suspect when replication cannot connect at all, not when data arrives late under asynchronous replication.
- ✗
Incorrect replication configuration using a read replica instead of a standby
Why it's wrong here
A read replica accepts writes only from its source and is not a failover target, so it cannot serve as the standby the recovery plan expects. Read replicas are the right design for offloading read traffic, not for cross-region disaster recovery requiring promotion.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
This CV0-004 practice question is part of Courseiva's free CompTIA 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 CV0-004 exam.