Quick Answer
The answer is to store logs in Amazon S3 and use S3 Select for queries, as this combination delivers the most cost-effective log storage with S3 and S3 Select for 90-day retention of 1 TB per day. S3’s low-cost object storage, combined with lifecycle policies to automatically expire data after 90 days, eliminates the need for expensive, provisioned databases, while S3 Select runs SQL-like analytical queries directly on the data without spinning up a separate compute engine, drastically reducing operational overhead and query costs. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your ability to choose storage-optimized solutions over compute-heavy ones—a common trap is selecting Amazon Athena or Redshift Spectrum, which incur additional per-query or cluster costs for infrequent analytics. Remember the memory tip: “S3 Select skips the compute lift”—if your logs are cold and queries are periodic, let S3 do the filtering server-side.
This DBS-C01 practice question tests your understanding of workload-specific database design. 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 needs to store application logs for 90 days and run periodic analytical queries. The logs are generated at 1 TB per day. Which storage solution is most cost-effective?
Store logs in Amazon RDS for MySQL with partitioning.
Why wrong: RDS cost is high for 1 TB/day.
Store logs in Amazon Redshift with automatic compression.
Why wrong: Redshift is more expensive for raw log storage.
Store logs in Amazon DynamoDB with TTL for expiration.
Why wrong: DynamoDB is not ideal for large blobs.
Store logs in Amazon S3 and use S3 Select for queries.
S3 is cost-effective and S3 Select supports queries.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Store logs in Amazon S3 and use S3 Select for queries.
Amazon S3 is the most cost-effective storage solution for 90-day retention of 1 TB/day of application logs, as it offers low-cost object storage with lifecycle policies to automatically expire data after 90 days. S3 Select allows you to run analytical queries (e.g., filtering, aggregations) directly on the data stored in S3 using SQL-like statements, without needing to load data into a separate analytics engine, thus minimizing compute costs and operational overhead.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Store logs in Amazon RDS for MySQL with partitioning.
Why it's wrong here
RDS cost is high for 1 TB/day.
Store logs in Amazon Redshift with automatic compression.
Why it's wrong here
Redshift is more expensive for raw log storage.
Store logs in Amazon DynamoDB with TTL for expiration.
Why it's wrong here
DynamoDB is not ideal for large blobs.
Store logs in Amazon S3 and use S3 Select for queries.
Why this is correct
S3 is cost-effective and S3 Select supports queries.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates often over-engineer the solution by choosing a database or data warehouse (like Redshift or RDS) for log storage, forgetting that S3 with S3 Select is purpose-built for cost-effective storage and serverless querying of large datasets with minimal operational complexity.
Detailed technical explanation
S3 Select works by pushing down simple SQL predicates (e.g., SELECT, WHERE) to the S3 server side, which filters data before returning results, reducing network transfer and client-side processing. For log analytics, you can combine S3 Select with S3 Inventory and Athena for more complex queries, but for periodic simple queries, S3 Select avoids the overhead of spinning up a server or cluster. Lifecycle policies in S3 can transition objects to S3 Glacier Deep Archive after 90 days for even lower cost, but for active queries within the retention period, S3 Standard or S3 Intelligent-Tiering is appropriate.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Workload-Specific Database Design — This question tests Workload-Specific Database Design — Read the scenario before looking for a memorised answer..
The correct answer is: Store logs in Amazon S3 and use S3 Select for queries. — Amazon S3 is the most cost-effective storage solution for 90-day retention of 1 TB/day of application logs, as it offers low-cost object storage with lifecycle policies to automatically expire data after 90 days. S3 Select allows you to run analytical queries (e.g., filtering, aggregations) directly on the data stored in S3 using SQL-like statements, without needing to load data into a separate analytics engine, thus minimizing compute costs and operational overhead.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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