CV0-004 Security Practice Question
A cloud architect is designing a multi-tier application. The application tier needs to access a database, but the database should not be reachable from the internet. Which network security control should be used?
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
✓
Place the database in a private subnet and use a security group to allow traffic only from the application tier
Placing the database in a private subnet with no direct internet route ensures it is not reachable from the internet. Security groups can then allow inbound traffic only from the application tier's security group.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Place the database in a private subnet and use a security group to allow traffic only from the application tier
Why this is correct
A private subnet removes the database from internet routing, while a security group referencing the application tier as source enforces least-privilege access at the instance level. Together they satisfy the constraint that only the application tier may reach the database.
- ✗
Encrypt the database connection using TLS
Why it's wrong here
TLS encrypts data in transit between the application tier and the database, but encryption does not alter network reachability; an internet-facing database endpoint remains reachable. TLS suits protecting credentials and query data on an already-isolated connection. The stem requires removing internet routability, which private subnet placement provides.
- ✗
Use a VPN to connect the application tier to the database
Why it's wrong here
A VPN encrypts traffic in transit between endpoints but does not change the database's network placement, so an internet-routable database stays reachable. VPNs suit connecting on-premises networks or remote users to a cloud VPC. The requirement is subnet-level isolation, achieved by placing the database in a private subnet.
- ✗
Place the database in a public subnet with restrictive security groups
Why it's wrong here
A public subnet carries a route to an internet gateway, so the database remains externally reachable regardless of security group rules; security groups filter traffic but do not remove internet routability. Private subnets are the correct control here. Public subnets suit internet-facing load balancers or bastion hosts.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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