The answer is AWS Security Token Service (STS). This is the correct choice because STS is specifically designed to generate temporary S3 credentials with a configurable expiration period, such as 30 minutes, through the AssumeRole API call. These credentials are limited-privilege and time-bound, directly meeting the requirement for granting short-lived access to an S3 bucket without exposing long-term keys. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding of identity federation and temporary credential management, often appearing in questions about secure cross-account access or user impersonation. A common trap is confusing STS with IAM roles or Cognito identity pools—remember that STS is the core service for generating temporary tokens, while Cognito is for federated user identities. Memory tip: STS stands for "Short-Term Security," as in credentials that expire.
DVA-C02 Security Practice Question
This DVA-C02 practice question tests your understanding of security. 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 developer needs to generate temporary credentials for a user to access an S3 bucket for 30 minutes. Which AWS service should be used?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
AWS Security Token Service (STS)
AWS Security Token Service (STS) is the correct service for generating temporary, limited-privilege credentials to access AWS resources. It can issue credentials with a configurable expiration period, such as 30 minutes, via the AssumeRole API call. This directly meets the requirement for time-bound access to an S3 bucket.
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.
✗
IAM role
Why it's wrong here
IAM roles define permissions but STS generates the temporary credentials for assuming the role.
✗
Amazon Cognito
Why it's wrong here
Cognito identity pools can provide temporary credentials, but STS is simpler for this use case.
✗
AWS Key Management Service (KMS)
Why it's wrong here
KMS manages encryption keys, not temporary credentials.
✓
AWS Security Token Service (STS)
Why this is correct
STS issues temporary credentials that can be configured to expire in 30 minutes.
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 confuse IAM roles (a permission container) with the service that actually issues temporary credentials (STS), leading them to select Option A instead of D.
Detailed technical explanation
How to think about this question
STS issues credentials consisting of an Access Key ID, Secret Access Key, and Session Token, with a default lifetime of 1 hour but configurable from 15 minutes to 36 hours via the DurationSeconds parameter. The credentials are signed with a unique session token that must be included in all requests, ensuring they are only valid for the specified duration. In practice, developers often use STS to grant cross-account access or to federate users from an external identity provider without storing long-term keys.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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.
Security — This question tests Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: AWS Security Token Service (STS) — AWS Security Token Service (STS) is the correct service for generating temporary, limited-privilege credentials to access AWS resources. It can issue credentials with a configurable expiration period, such as 30 minutes, via the AssumeRole API call. This directly meets the requirement for time-bound access to an S3 bucket.
What should I do if I get this DVA-C02 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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Question Discussion
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