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DEA-C01 Data Operations and Support Practice Question

A data engineer is monitoring an Amazon Redshift cluster and notices that the 'WLM query wait time' metric is consistently high during peak hours. The cluster uses automatic WLM. The engineer wants to reduce query wait times without changing the cluster size. Which action is MOST effective?

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

✓

Enable concurrency scaling.

Enabling concurrency scaling (Option A) is the most effective action because it automatically adds transient cluster capacity during peak loads, allowing more queries to run concurrently without increasing wait times. This is specifically designed to reduce WLM query wait time. Option B (manual WLM) requires tuning and does not add capacity. Option C (increasing max queries per queue) could increase concurrency but may lead to resource contention and longer wait times if the cluster is already saturated. Option D (short query acceleration) prioritizes short queries, which does not address overall wait times for all queries. Therefore, A is correct.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • ✓

    Enable concurrency scaling.

    Why this is correct

    Concurrency scaling adds transient Redshift compute capacity automatically when queries queue, directly cutting WLM query wait time during peak hours. It absorbs burst concurrency without resizing the cluster, satisfying the constraint of reducing wait times at unchanged cluster size.

  • ✗

    Change WLM to manual mode and increase the number of queues.

    Why it's wrong here

    Manual WLM removes automatic concurrency and memory tuning, so queues cannot adapt to changing workloads and waits typically worsen. Automatic WLM already allocates resources dynamically. Manual mode is chosen when you need fixed, predictable queue behaviour for specific workload isolation, not to cut wait times.

  • ✗

    Increase the maximum number of queries per queue.

    Why it's wrong here

    Raising the per-queue query limit lets more concurrent queries compete for the same slots, increasing contention and wait time. Automatic WLM already balances concurrency against memory. That setting suits throughput tuning when queues are underused, not when queries are already queuing during peak load.

  • ✗

    Enable short query acceleration (SQA).

    Why it's wrong here

    SQA only routes short-running queries to a dedicated space; it does not add capacity for the long queries causing the waits. Automatic WLM already prioritises short queries. SQA is the right choice when short queries are starved behind long ones, not when overall concurrency exceeds available slots.

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Same concept, more angles

1 more way this is tested on DEA-C01

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. A data engineer is monitoring an Amazon Redshift cluster and notices that queries are taking longer than expected. The engineer checks the system tables and sees that many queries are waiting for 'WLM' resources. What is the most likely cause and recommended fix?

hard
  • A.The table sort keys are poorly designed; recreate tables with better sort keys.
  • B.The distribution style is set to ALL; change to KEY distribution.
  • ✓ C.The WLM queue concurrency is set too low; increase the concurrency level.
  • D.The cluster is running low on disk space; resize the cluster.

Why C: When queries wait on WLM resources, it means they are queued because the workload management (WLM) queue does not have enough concurrency slots to run them. Increasing the concurrency level of the WLM queue allows more queries to run simultaneously, reducing wait time. This is the most direct fix for WLM queue waits.

JA

Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

This DEA-C01 practice question is part of Courseiva's free Amazon Web Services 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 DEA-C01 exam.