DP-300 Practice Question: Monitor, configure, and optimize database resources
You manage an Azure SQL Database that uses the Business Critical service tier. A critical reporting query normally completes in under 5 seconds but occasionally takes over 60 seconds. You observe that during these slow executions, the query uses a different execution plan that performs a large number of physical reads. You need to ensure that the fast plan is used consistently for this query. What should you do?
⚠ Common exam trap
The trap here is assuming that enabling automatic tuning will always force the exact fast plan, but automatic tuning only forces the last known good plan reactively and may not select the specific plan you want.
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 Query Store to force the fast execution plan for the query.
Query Store captures all plans generated for a query and provides a mechanism to force a specific plan. When a query occasionally uses a suboptimal plan that causes high physical reads, you can identify the fast plan in Query Store and force it, ensuring consistent performance. This approach is native to Azure SQL Database and allows you to monitor and easily revert if needed.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Increase the database's compute size to reduce physical reads.
Why it's wrong here
Scaling up compute may improve overall performance but does not address the root cause: inconsistent plan selection. The slow plan performs many physical reads due to poor choices such as a bad join order or missing index usage, and more CPU or memory will not prevent that plan from being chosen. It is a costly workaround rather than a targeted fix.
- ✗
Enable automatic tuning FORCE_LAST_GOOD_PLAN on the database.
Why it's wrong here
FORCE_LAST_GOOD_PLAN automatically forces the last known good plan when Query Store detects a regression, but it may not choose the specific fast plan you identified, and it works reactively after a regression is detected. It cannot guarantee that the fast plan is used consistently from the start, so it is less deterministic than manually forcing the plan.
- ✗
Create a plan guide using sp_create_plan_guide for the query.
Why it's wrong here
Plan guides can force a plan, but they are more complex to manage and are not integrated with Query Store's plan forcing mechanism. In Azure SQL Database, Query Store plan forcing is the recommended approach for this scenario because it ties directly into the captured plan and allows easy monitoring and removal.
- ✓
Use Query Store to force the fast execution plan for the query.
Why this is correct
Query Store captures multiple plans for a query and allows you to force a specific plan. By identifying the fast plan in Query Store and forcing it, you ensure that the query consistently uses that plan, avoiding the slow plan that causes excessive physical reads. This is the most direct and supported method in Azure SQL Database.
Go deeper
Related to this question
Learn chapter
Implementing High Availability for Azure SQL Databases
Key term
Query Store
Query Store is a built-in SQL Server feature that captures and stores a history of query execution plans and performance data for easy monitoring and troubleshooting.
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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Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Microsoft exam blueprint
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