AZ-400 Implement an instrumentation strategy Practice Question
You are troubleshooting an intermittent performance issue in a web application. Application Insights shows a high number of failed dependency calls to Azure SQL Database. The errors are SqlException with error code -2 (timeout). What is the most likely cause and recommended fix?
⚠ Common exam trap
Watch out — candidates often confuse a connection timeout (error -2) with a query timeout or resource throttling, leading them to choose DTU scaling or deadlock solutions instead of recognizing the connection pool exhaustion pattern.
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 application is exhausting the connection pool; increase Max Pool Size in the connection string.
A is correct because SqlException with error code -2 indicates a connection timeout, which in a high-traffic scenario is most commonly caused by the application exhausting the connection pool. When all connections in the pool are in use and the wait time for a free connection exceeds the Connect Timeout (default 15 seconds), new requests fail with this error. Increasing Max Pool Size in the connection string (e.g., Max Pool Size=200) allows more concurrent connections, reducing contention.
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 application is exhausting the connection pool; increase Max Pool Size in the connection string.
Why this is correct
Connection pool exhaustion occurs when the application requests more connections than the configured Max Pool Size, forcing new requests to wait for a free connection until the connection timeout threshold is reached, which manifests as intermittent timeouts under load; increasing Max Pool Size or ensuring connections are properly disposed can resolve this.
- ✗
The SQL Server firewall is blocking the application IP; add a firewall rule.
Why it's wrong here
A SQL Server firewall rule blocks traffic at the network or login layer, producing an immediate connection failure or login error before the application can acquire a connection; it does not cause wait-based timeouts after the connection pool is already in use, so this is not the cause of intermittent timeout symptoms.
- ✗
The database is experiencing deadlocks; enable read committed snapshot isolation.
Why it's wrong here
Deadlocks are detected by SQL Server's lock manager and immediately terminated with error 1205, not by the application waiting for a connection timeout; enabling read committed snapshot isolation can reduce deadlock occurrences but does not affect connection pool timeout behavior.
- ✗
The database DTU limit is being exceeded; scale up the service tier.
Why it's wrong here
Exceeding the DTU limit causes Azure SQL Database to throttle or queue queries, typically surfacing as performance degradation or resource-wait errors such as DTU waits, not as connection timeout exceptions from the application; scaling the service tier would not address a connection pool exhaustion issue.
Go deeper
Related to this question
Learn chapter
Introduction to DevOps and Azure DevOps
Key term
Application Insights
Application Insights is an Azure monitoring service that helps developers detect, diagnose, and understand issues in live web applications by collecting telemetry data like requests, exceptions, and performance counters.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-400 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 AZ-400 exam.