DBS-C01 Workload-Specific Database Design Practice Question
A company is designing a multi-tenant SaaS application on Amazon RDS for PostgreSQL. Tenants have vastly different data sizes and access patterns. The current design uses a separate schema per tenant, but some tenants experience slow queries while others are fine. Which approach would best isolate tenant performance and simplify management?
⚠ Common exam trap
Watch out — candidates often confuse logical data isolation (RLS or schema-per-tenant) with performance isolation, assuming that indexing or connection pooling can solve resource contention, when in fact only physical separation (separate databases) guarantees that one tenant's workload does not impact another's performance.
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
✓
Use a separate database per tenant.
Using a separate database per tenant provides the strongest resource isolation at the database instance level. This design prevents noisy neighbors—tenants with large data volumes or heavy access patterns from degrading the performance of other tenants—and simplifies management tasks such as backup, restore, and point-in-time recovery on a per-tenant basis. Amazon RDS for PostgreSQL supports multiple databases within a single DB instance, and each database operates with its own catalog, tables, and connection pool, ensuring that query execution and memory allocation are not shared across tenants.
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 row-level security (RLS) policies within a single schema to restrict tenant data access.
Why it's wrong here
RLS provides security isolation but not performance isolation; all queries share the same database resources.
- ✗
Keep the current schema design and add a tenant_id index to all tables.
Why it's wrong here
Indexing does not isolate performance; queries still compete for the same database resources.
- ✓
Use a separate database per tenant.
Why this is correct
Separate databases provide strong performance isolation and allow per-tenant resource allocation and backup.
- ✗
Use Amazon RDS Proxy to manage connections and improve performance.
Why it's wrong here
RDS Proxy handles connection pooling but does not isolate performance between tenants.
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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.