- A
Use RDS for PostgreSQL with pg_partman to partition data by tenant and implement connection limits per tenant using PostgreSQL advisory locks.
Why wrong: Partitioning does not limit connections; advisory locks are not for connection management.
- B
Replace RDS with Amazon Aurora PostgreSQL and use Aurora Auto Scaling to handle connection spikes.
Why wrong: Auto Scaling adjusts capacity, but does not isolate tenants; noisy tenants still affect others.
- C
Move all tenants to a single RDS instance with separate schemas and use RDS Proxy to manage connections.
Why wrong: This does not isolate noisy tenants; one tenant can still consume resources.
- D
Create separate RDS instances for large tenants and use a single RDS instance for small tenants, with PgBouncer connection pooling per instance.
This isolates noisy tenants on dedicated instances while consolidating small tenants, balancing isolation and cost.
Quick Answer
The answer is to create separate RDS instances for large tenants and a single RDS instance for small tenants, with PgBouncer connection pooling per instance. This design is correct because it directly addresses multi-tenant connection management by isolating noisy tenants into their own compute and connection resources, preventing a single tenant’s connection surge from driving up CPU and connection count on shared infrastructure. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of workload-specific database design for SaaS applications, where PgBouncer acts as a lightweight connection broker but cannot isolate resource contention across tenants on the same RDS instance. A common trap is to assume that simply adding more PgBouncer instances or increasing pool sizes will solve the problem, but the real fix is architectural separation of noisy workloads. Memory tip: “Isolate the noise, pool the rest” — separate large tenants at the instance level, then pool connections per instance with PgBouncer.
DBS-C01 Workload-Specific Database Design Practice Question
This DBS-C01 practice question tests your understanding of workload-specific database design. 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 multi-tenant SaaS application on Amazon RDS for PostgreSQL. Each tenant has an isolated database. Recently, the application experienced a sudden increase in connection errors and slow query performance. Amazon RDS instance metrics show high CPU utilization and a high number of database connections. The application uses connection pooling with PgBouncer running on an EC2 instance. The team suspects the issue is due to a few noisy tenants opening too many connections. The current architecture uses one RDS instance per tenant. The company wants to optimize for workload-specific database design to handle noisy tenants without affecting other tenants. Which design should be implemented to isolate noisy tenants and reduce costs?
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
Create separate RDS instances for large tenants and use a single RDS instance for small tenants, with PgBouncer connection pooling per instance.
Option D is correct because it directly addresses the need to isolate noisy tenants by creating separate RDS instances for large (noisy) tenants while consolidating small tenants onto a single instance, each fronted by its own PgBouncer connection pool. This design prevents a single tenant's connection surge from affecting others, optimizes costs by avoiding over-provisioning for all tenants, and aligns with workload-specific database design principles for multi-tenant SaaS on RDS for PostgreSQL.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use RDS for PostgreSQL with pg_partman to partition data by tenant and implement connection limits per tenant using PostgreSQL advisory locks.
Why it's wrong here
Partitioning does not limit connections; advisory locks are not for connection management.
- ✗
Replace RDS with Amazon Aurora PostgreSQL and use Aurora Auto Scaling to handle connection spikes.
Why it's wrong here
Auto Scaling adjusts capacity, but does not isolate tenants; noisy tenants still affect others.
- ✗
Move all tenants to a single RDS instance with separate schemas and use RDS Proxy to manage connections.
Why it's wrong here
This does not isolate noisy tenants; one tenant can still consume resources.
- ✓
Create separate RDS instances for large tenants and use a single RDS instance for small tenants, with PgBouncer connection pooling per instance.
Why this is correct
This isolates noisy tenants on dedicated instances while consolidating small tenants, balancing isolation and cost.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may assume a single shared database with connection pooling (Option C) or a fully managed scaling solution (Option B) can solve noisy neighbor problems, but the DBS-C01 exam tests the understanding that workload isolation requires separate database instances or dedicated resources, not just connection management or auto-scaling of a shared cluster.
Detailed technical explanation
How to think about this question
PgBouncer uses transaction-level pooling (session pooling is default but transaction pooling is common for SaaS) to multiplex many client connections into a smaller number of database connections, reducing connection overhead. In this scenario, placing PgBouncer per instance ensures that connection limits are enforced at the pool level, and separate RDS instances for large tenants provide hardware-level isolation via dedicated vCPU and memory, preventing noisy neighbors from consuming shared resources. This design mirrors a 'pool-per-tenant' pattern often used in high-density multi-tenant SaaS to balance isolation and cost.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this DBS-C01 question test?
Workload-Specific Database Design — This question tests Workload-Specific Database Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create separate RDS instances for large tenants and use a single RDS instance for small tenants, with PgBouncer connection pooling per instance. — Option D is correct because it directly addresses the need to isolate noisy tenants by creating separate RDS instances for large (noisy) tenants while consolidating small tenants onto a single instance, each fronted by its own PgBouncer connection pool. This design prevents a single tenant's connection surge from affecting others, optimizes costs by avoiding over-provisioning for all tenants, and aligns with workload-specific database design principles for multi-tenant SaaS on RDS for PostgreSQL.
What should I do if I get this DBS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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