- A
Upgrade to a larger single Redis node instance type to handle the load.
Why wrong: Scaling vertically may temporarily help but does not address the need for high availability and sharding.
- B
Replace Redis with DynamoDB for the leaderboard, using a global secondary index on score.
Why wrong: DynamoDB is not optimized for real-time leaderboard operations like sorted sets.
- C
Use a Redis Cluster with multiple shards. Enable AOF persistence and use a read replica for the leaderboard queries.
Redis Cluster distributes data across shards, reducing load per node. Read replicas can handle queries, and AOF ensures durability.
- D
Use ElastiCache for Redis with cluster mode disabled and enable Multi-AZ.
Why wrong: Cluster mode disabled means single node, Multi-AZ provides failover but not sharding.
DBS-C01 Workload-Specific Database Design Practice Question
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 gaming company uses Amazon ElastiCache for Redis as a leaderboard for real-time game scores. The leaderboard is updated frequently by millions of users. The application uses sorted sets with player scores. Recently, the leaderboard update latency increased and the cache evictions spiked. The company needs to ensure low-latency updates and high availability. The current setup is a single Redis node. Which design should be implemented?
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 Redis Cluster with multiple shards. Enable AOF persistence and use a read replica for the leaderboard queries.
Option C is correct because Redis Cluster with multiple shards distributes the write load across shards, reducing per-node pressure and evictions. Enabling AOF persistence ensures durability, while using a read replica for leaderboard queries offloads read traffic from the primary shard, maintaining low-latency updates. This design provides both horizontal scaling and high availability, addressing the increased update latency and eviction spikes.
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.
- ✗
Upgrade to a larger single Redis node instance type to handle the load.
Why it's wrong here
Scaling vertically may temporarily help but does not address the need for high availability and sharding.
- ✗
Replace Redis with DynamoDB for the leaderboard, using a global secondary index on score.
Why it's wrong here
DynamoDB is not optimized for real-time leaderboard operations like sorted sets.
- ✓
Use a Redis Cluster with multiple shards. Enable AOF persistence and use a read replica for the leaderboard queries.
Why this is correct
Redis Cluster distributes data across shards, reducing load per node. Read replicas can handle queries, and AOF ensures durability.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use ElastiCache for Redis with cluster mode disabled and enable Multi-AZ.
Why it's wrong here
Cluster mode disabled means single node, Multi-AZ provides failover but not sharding.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may assume Multi-AZ (Option D) alone solves high availability and performance, but without sharding (cluster mode enabled), a single node remains a bottleneck for write-heavy workloads, and evictions will continue.
Detailed technical explanation
How to think about this question
Redis Cluster uses a hash slot mechanism (16,384 slots) to distribute keys across shards, allowing linear scaling of write throughput. The sorted set operations (ZADD, ZINCRBY) are atomic per key, and with sharding, each shard handles a subset of players, reducing contention. AOF persistence with 'appendfsync everysec' balances durability and performance, while read replicas in cluster mode can serve read-only commands (e.g., ZRANGE) without affecting primary write latency, though they may return slightly stale data in the event of a failover.
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
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.
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FAQ
Questions learners often ask
What does this DBS-C01 question test?
Workload-Specific Database Design — This question tests Workload-Specific Database Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use a Redis Cluster with multiple shards. Enable AOF persistence and use a read replica for the leaderboard queries. — Option C is correct because Redis Cluster with multiple shards distributes the write load across shards, reducing per-node pressure and evictions. Enabling AOF persistence ensures durability, while using a read replica for leaderboard queries offloads read traffic from the primary shard, maintaining low-latency updates. This design provides both horizontal scaling and high availability, addressing the increased update latency and eviction spikes.
What should I do if I get this DBS-C01 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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Last reviewed: Jun 24, 2026
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