- A
Update the application's connection string to point to the new writer endpoint.
Explicitly updating the endpoint ensures immediate connectivity.
- B
Reboot the new primary instance to reset connections.
Why wrong: Rebooting causes additional downtime and is unnecessary.
- C
Update the security group to allow inbound traffic from the application.
Why wrong: Security group configuration remains valid after failover.
- D
Wait for DNS propagation and flush the application's DNS cache.
DNS changes propagate automatically; flushing cache speeds up resolution.
- E
Create a read replica and promote it to a new primary.
Why wrong: Creating a read replica is unnecessary; a primary already exists.
Question 1,209 of 1,730
RDS Failover Connectivity Recovery
This DBS-C01 practice question tests your understanding of management and operations. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company is running an Amazon RDS for MySQL instance with Multi-AZ. The primary instance in us-east-1a fails, and the standby in us-east-1b is promoted. The application cannot connect after failover. Which TWO steps should the database administrator take to restore connectivity?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"primary"Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
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
✓
Update the application's connection string to point to the new writer endpoint.
Option A is correct because after failover, the application may be connecting to the old primary instance endpoint. Updating the connection string to the DNS writer endpoint (which automatically points to the new primary) ensures connectivity. Option D is correct because after failover, the writer endpoint's DNS record updates to the new primary's IP. Waiting for propagation and flushing the DNS cache ensures the application resolves the updated IP. Option B is incorrect because rebooting is not required and would cause further disruption. Option C is incorrect because the security group already permits traffic from the application; the issue is DNS resolution, not network access. Option E is incorrect because creating a read replica does not solve the connectivity issue and is unnecessary for a Multi-AZ failover.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Update the application's connection string to point to the new writer endpoint.
Why this is correct
Explicitly updating the endpoint ensures immediate connectivity.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
- ✗
Reboot the new primary instance to reset connections.
Why it's wrong here
Rebooting causes additional downtime and is unnecessary.
- ✗
Update the security group to allow inbound traffic from the application.
Why it's wrong here
Security group configuration remains valid after failover.
- ✓
Wait for DNS propagation and flush the application's DNS cache.
Why this is correct
DNS changes propagate automatically; flushing cache speeds up resolution.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
- ✗
Create a read replica and promote it to a new primary.
Why it's wrong here
Creating a read replica is unnecessary; a primary already exists.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
- Standard ACLs match source addresses.
- Extended ACLs can match source, destination, protocol and ports.
- The first matching ACL entry is used.
- There is usually an implicit deny at the end.
TExam Day Tips
- Check inbound versus outbound direction.
- Read the ACL from top to bottom.
- Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
Visual reference
Quick reference
Common DNS Record Types
| Record | Purpose | Example |
|---|---|---|
| A | IPv4 address mapping | example.com → 93.184.216.34 |
| AAAA | IPv6 address mapping | example.com → 2606:2800::1 |
| CNAME | Alias to another hostname | www → example.com |
| MX | Mail server for domain | example.com → mail.example.com (priority 10) |
| TXT | Text data (SPF, DKIM, verification) | v=spf1 include:_spf.example.com ~all |
| NS | Authoritative name servers | example.com NS ns1.example.com |
| PTR | Reverse DNS (IP → hostname) | 34.216.184.93.in-addr.arpa → example.com |
| SOA | Zone authority record | Primary NS, admin email, serial, TTL defaults |
What to study next
Got this wrong? Here's your next step.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DBS-C01 ACL questions on filtering logic and placement.
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FAQ
Questions learners often ask
What does this DBS-C01 question test?
Management and Operations — This question tests Management and Operations — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Update the application's connection string to point to the new writer endpoint. — Option A is correct because after failover, the application may be connecting to the old primary instance endpoint. Updating the connection string to the DNS writer endpoint (which automatically points to the new primary) ensures connectivity. Option D is correct because after failover, the writer endpoint's DNS record updates to the new primary's IP. Waiting for propagation and flushing the DNS cache ensures the application resolves the updated IP. Option B is incorrect because rebooting is not required and would cause further disruption. Option C is incorrect because the security group already permits traffic from the application; the issue is DNS resolution, not network access. Option E is incorrect because creating a read replica does not solve the connectivity issue and is unnecessary for a Multi-AZ failover.
What should I do if I get this DBS-C01 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DBS-C01 ACL questions on filtering logic and placement.
Are there clue words in this question I should notice?
Yes — watch for: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
What is the key concept behind this question?
Standard ACLs match source addresses.
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Last reviewed: Jun 20, 2026
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