DBS-C01 Deployment and Migration Practice Question
A company is deploying a new web application that uses Amazon RDS for MySQL. To improve read performance, they add a read replica. However, the application reports stale data. What is the most likely cause?
⚠ Common exam trap
It's easy for candidates to confuse asynchronous replication with synchronous replication, assuming the replica always has the latest data, or they incorrectly attribute the issue to geographic distance or connection pooling rather than the fundamental replication lag inherent in MySQL's async model.
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
✓
The replication is asynchronous and there is replication lag.
Amazon RDS for MySQL uses asynchronous replication for read replicas. The primary instance commits writes and then sends the binary log (binlog) events to the replica, which applies them. This asynchronous nature introduces replication lag, meaning the replica may not have the most recent writes. If the application reads from the replica before the lag is resolved, it will see stale (older) data.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The application is using a connection pool that caches connections to the primary.
Why it's wrong here
Connection pooling does not cause stale data.
- ✗
The read replica is in a different AWS Region.
Why it's wrong here
Cross-region replicas have more lag but stale data can happen even in same region.
- ✓
The replication is asynchronous and there is replication lag.
Why this is correct
Asynchronous replication causes eventual consistency.
- ✗
The application is reading from the replica before the write is committed on the primary.
Why it's wrong here
Write is committed on primary; replica lag is the issue.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.