The answer is that the load balancer is sending write requests to standby nodes, which cannot handle writes. In a Vault cluster using the Raft storage backend, only the elected leader node can process write operations like creating secrets or policies; standby nodes serve reads and forward writes to the leader. When the load balancer distributes traffic to all three nodes without considering leadership, a write hitting a standby fails with a 502 Bad Gateway error because the standby cannot process the write locally, and the load balancer may mishandle the forwarded response or timeout. On the HashiCorp Vault Associate VA-003 exam, this scenario tests your understanding of cluster leadership and load balancer configuration—a common trap is assuming all nodes are equal for writes. Remember the memory tip: "Writes need the leader; standbys only read her."
VA-003 Explain Vault architecture Practice Question
This VA-003 practice question tests your understanding of explain vault architecture. 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 Vault in a single cluster with three nodes using the Raft storage backend. The nodes are behind a load balancer that distributes traffic to all nodes. The operations team notices that occasionally, write operations (e.g., writing a secret or creating a policy) fail with a '502 Bad Gateway' error, while read operations succeed. The Vault audit logs show no errors. The load balancer health checks are configured to check the /v1/sys/health endpoint with a 200 response expected. The Vault nodes are all unsealed and the cluster is healthy. Which of the following is the most likely cause of the intermittent write failures?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The load balancer is sending write requests to standby nodes, which cannot handle writes.
In a Vault cluster with Raft storage, only the elected leader node can handle write operations (e.g., writing secrets, creating policies). Standby nodes serve read requests and forward writes to the leader. If the load balancer distributes traffic to all nodes without considering leadership, write requests sent to a standby node will fail with a 502 Bad Gateway error because the standby cannot process the write locally and the load balancer may not properly handle the forwarded response or timeout.
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.
✗
The Raft storage backend does not support write operations.
Why it's wrong here
Raft supports writes, but only on the leader.
✓
The load balancer is sending write requests to standby nodes, which cannot handle writes.
Why this is correct
Only the active node can process writes; standby nodes return a 502.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The load balancer is not configured to use the /v1/sys/leader endpoint for routing.
Why it's wrong here
Even if the load balancer used the leader endpoint, the issue is that standby nodes reject writes, not that routing is incorrect.
✗
One of the Vault nodes is sealed, causing write requests to fail.
Why it's wrong here
The problem states all nodes are unsealed.
Common exam traps
Common exam trap: answer the scenario, not the keyword
HashiCorp often tests the misconception that all Vault nodes in a cluster can handle writes equally, but in reality only the leader node processes write operations; the trap here is assuming that a healthy, unsealed node can always accept writes.
Detailed technical explanation
How to think about this question
Vault's Raft storage backend uses a leader-follower model where only the leader can accept writes; followers forward write requests to the leader via a redirect or proxy. The /v1/sys/health endpoint returns a 200 for both leader and standby nodes (by default), so health checks alone cannot distinguish leader from standby. A common best practice is to configure the load balancer to route write operations only to the leader by checking /v1/sys/leader or using a separate listener for writes, or to enable Vault's built-in request forwarding (which requires proper configuration of cluster addresses).
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 practitioner preparing for the VA-003 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Explain Vault architecture — This question tests Explain Vault architecture — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The load balancer is sending write requests to standby nodes, which cannot handle writes. — In a Vault cluster with Raft storage, only the elected leader node can handle write operations (e.g., writing secrets, creating policies). Standby nodes serve read requests and forward writes to the leader. If the load balancer distributes traffic to all nodes without considering leadership, write requests sent to a standby node will fail with a 502 Bad Gateway error because the standby cannot process the write locally and the load balancer may not properly handle the forwarded response or timeout.
What should I do if I get this VA-003 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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