The correct fix is to update the Docker image to include the latest MySQL client libraries that support TLS 1.2. This resolves the SSL connection error between ECS Fargate and RDS MySQL because the error “protocol version mismatch” indicates the MySQL client inside the container is using an outdated TLS version that RDS no longer accepts—RDS requires TLS 1.2 or higher for encrypted connections. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding that enabling SSL on RDS is not enough; the application’s client libraries must also support the required TLS version. A common trap is to focus on security group rules or connection strings, but the root cause is a client-side library limitation. Memory tip: when you see “protocol version mismatch” in an ECS-to-RDS SSL error, think “client library too old—update the image, not the config.”
DOP-C02 Security and Compliance Practice Question
This DOP-C02 practice question tests your understanding of security and compliance. 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 runs a production application on Amazon ECS with Fargate launch type. The application uses an RDS MySQL database. The security team requires that all traffic between the application and the database be encrypted in transit. Currently, the database security group allows inbound traffic from the ECS tasks' security group on port 3306 (MySQL). The application uses the standard MySQL client connection without SSL. After enabling SSL on the RDS instance, the application starts failing to connect. The error logs show 'SSL connection error: protocol version mismatch'. The application runs on a custom Docker image based on Amazon Linux 2. The DevOps engineer needs to fix the connection issue. Which course of action should the engineer take?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Update the Docker image to include the latest MySQL client libraries that support TLS 1.2.
The error indicates that the MySQL client in the container does not support the TLS version required by RDS. The simplest solution is to modify the application connection string to use the '--ssl-mode=REQUIRED' flag or equivalent, but the error persists even after that. The actual fix is to update the MySQL client libraries in the container image to a version that supports TLS 1.2, as RDS requires TLS 1.2 or higher. Alternatively, the engineer can configure RDS to accept TLS 1.0, but that is not secure. Changing the security group or using SSH tunneling does not address the TLS version mismatch.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 Docker image to include the latest MySQL client libraries that support TLS 1.2.
Why this is correct
Fixes the protocol version mismatch by using a client that supports required TLS version.
Related concept
Static NAT maps one inside address to one outside address.
✗
Update the application code to connect using SSL with the --ssl-mode=REQUIRED flag.
Why it's wrong here
The error is a protocol version mismatch, not missing SSL flag.
✗
Modify the RDS parameter group to allow TLS 1.0 and 1.1.
Why it's wrong here
This weakens security and may not be allowed by policy.
✗
Create a VPC peering connection and route traffic through a VPN.
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DOP-C02 NAT questions on configuration and troubleshooting.
Security and Compliance — This question tests Security and Compliance — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Update the Docker image to include the latest MySQL client libraries that support TLS 1.2. — The error indicates that the MySQL client in the container does not support the TLS version required by RDS. The simplest solution is to modify the application connection string to use the '--ssl-mode=REQUIRED' flag or equivalent, but the error persists even after that. The actual fix is to update the MySQL client libraries in the container image to a version that supports TLS 1.2, as RDS requires TLS 1.2 or higher. Alternatively, the engineer can configure RDS to accept TLS 1.0, but that is not secure. Changing the security group or using SSH tunneling does not address the TLS version mismatch.
What should I do if I get this DOP-C02 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DOP-C02 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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