- A
Persist session data in Cloud SQL to ensure durability.
Why wrong: Using a relational database for session storage introduces latency and a single point of failure; it is not a stateless design pattern.
- B
Offload session state to the user's browser using encrypted cookies.
Storing session data on the client side through cookies eliminates server-side state, making the application fully stateless.
- C
Deploy the application across multiple regional managed instance groups.
Why wrong: Regional MIGs enhance availability and resilience, but they do not address the statelessness requirement.
- D
Store session state in an external cache such as Memorystore.
External caching separates session data from compute, enabling any instance to handle requests and facilitating stateless scaling.
- E
Use sticky sessions to maintain client affinity.
Why wrong: Sticky sessions couple a client to a specific backend instance, hindering horizontal scaling and fault tolerance.
Quick Answer
The answer is to store session state in an external cache like Memorystore. This practice ensures the application remains stateless by decoupling session data from individual compute instances, allowing any instance to handle any request without relying on local memory. For horizontal scaling, stateless web application practices require that no critical data is tied to a specific server; externalizing session state to a fast, in-memory data store like Memorystore or Redis eliminates the need for sticky sessions, which would otherwise prevent true elasticity. On the Google Professional Cloud Developer exam, this concept tests your understanding of designing for autoscaling and fault tolerance, often appearing in scenarios where a candidate must choose between sticky sessions, database persistence, or external caching. A common trap is selecting Cloud SQL for session persistence, which introduces latency and a single point of failure, or assuming regional managed instance groups alone solve statelessness. Remember the mnemonic: “Cache the state, don’t stick the fate”—always offload session data to an external cache or the client to keep your web app horizontally scalable.
PCD Practice Question: Designing highly scalable, available, and reliable cloud-native applications
This PCD practice question tests your understanding of designing highly scalable, available, and reliable cloud-native applications. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 designing a web application that must scale horizontally to handle variable traffic. Which two practices should they implement to ensure the application is stateless and can scale without issues?
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
Offload session state to the user's browser using encrypted cookies.
To achieve statelessness, session state should either be stored in an external cache (e.g., Memorystore) or offloaded to the client (e.g., using cookies). Sticky sessions tie a client to a specific instance, preventing scaling. Using a database like Cloud SQL for session persistence creates a bottleneck. Regional managed instance groups improve availability but do not directly address statelessness.
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.
- ✗
Persist session data in Cloud SQL to ensure durability.
Why it's wrong here
Using a relational database for session storage introduces latency and a single point of failure; it is not a stateless design pattern.
- ✓
Offload session state to the user's browser using encrypted cookies.
Why this is correct
Storing session data on the client side through cookies eliminates server-side state, making the application fully stateless.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Deploy the application across multiple regional managed instance groups.
Why it's wrong here
Regional MIGs enhance availability and resilience, but they do not address the statelessness requirement.
- ✓
Store session state in an external cache such as Memorystore.
Why this is correct
External caching separates session data from compute, enabling any instance to handle requests and facilitating stateless scaling.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use sticky sessions to maintain client affinity.
Why it's wrong here
Sticky sessions couple a client to a specific backend instance, hindering horizontal scaling and fault tolerance.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- 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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
Identify which PCD exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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Designing highly scalable, available, and reliable cloud-native applications — study guide chapter
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FAQ
Questions learners often ask
What does this PCD question test?
Designing highly scalable, available, and reliable cloud-native applications — This question tests Designing highly scalable, available, and reliable cloud-native applications — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Offload session state to the user's browser using encrypted cookies. — To achieve statelessness, session state should either be stored in an external cache (e.g., Memorystore) or offloaded to the client (e.g., using cookies). Sticky sessions tie a client to a specific instance, preventing scaling. Using a database like Cloud SQL for session persistence creates a bottleneck. Regional managed instance groups improve availability but do not directly address statelessness.
What should I do if I get this PCD question wrong?
Identify which PCD exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jun 24, 2026
This PCD practice question is part of Courseiva's free Google Cloud 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 PCD exam.
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