DP-300 Practice Question: Monitor, configure, and optimize database resources
You are monitoring an Azure SQL Database using dynamic management views (DMVs). You run a query against `sys.dm_exec_query_stats` to find the top 10 queries by total worker time. Several queries show high worker time but low logical reads. The database is not experiencing any blocking or deadlocks. What is the most likely cause of the high worker time?
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
✓
The queries are CPU-bound due to inefficient query plans.
High worker time (CPU time) with low logical reads indicates that the queries are CPU-bound rather than I/O-bound. Inefficient query plans, such as those with large hash joins, sorts, or non-sargable predicates, can cause excessive CPU consumption without generating many logical reads. Option A is incorrect because parameter sniffing typically leads to varying plan quality, but the consistent high worker time across multiple queries suggests a systematic plan efficiency issue, not necessarily parameter sniffing. Option B is incorrect because memory pressure would cause increased I/O activity (lazy writes) which is not observed with low logical reads. Option C is incorrect because transaction log writes are I/O operations and would not cause high worker time with low I/O.
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 queries suffer from parameter sniffing leading to suboptimal plans.
Why it's wrong here
Parameter sniffing produces a suboptimal cached plan, which typically manifests as elevated logical reads from a poor scan or seek choice; the stem explicitly reports low logical reads. Sniffing would be the answer when a plan's reads and duration spike for particular parameter values, but CPU-bound computation with few reads indicates something else.
- ✗
The queries are experiencing memory pressure causing excessive lazy writes.
Why it's wrong here
Lazy writes flush dirty buffer pages to disk and are measured through wait types and page-life-expectancy DMVs, not worker time; they also accompany high logical reads, which the stem reports as low. Memory pressure would be the answer if the stem showed PAGEIOLATCH or RESOURCE_SEMAPHORE waits, but high worker time with low reads points to CPU-bound work.
- ✗
The queries are waiting on transaction log writes.
Why it's wrong here
Waiting on transaction log writes surfaces as WRITELOG waits and elevated write latency, and it accompanies data modification activity rather than pure CPU consumption. Log-write contention would be the answer if the stem showed WRITELOG waits or slow commits, but high worker time with low logical reads indicates CPU-intensive computation instead.
- ✓
The queries are CPU-bound due to inefficient query plans.
Why this is correct
High worker time with low logical reads indicates CPU consumption rather than I/O. Inefficient plans, such as scans, bad cardinality estimates or missing indexes causing repeated CPU-heavy operations, burn worker time without many page reads, and no blocking or deadlocks were reported.
Go deeper
Related to this question
Learn chapter
Monitoring Database Performance with Azure Tools
Key term
Azure SQL Performance Tuning
Azure SQL Performance Tuning is the process of optimizing the speed and efficiency of queries and database operations in Microsoft Azure SQL Database or SQL Managed Instance to reduce latency and improve throughput.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DP-300 practice question is part of Courseiva's free Microsoft 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 DP-300 exam.