Debugging scenarioMedium~10 minAzure Production Incident Debugging Essentials / 14 of 15

Interview question

A production .NET API is running, but Application Insights shows missing or incomplete telemetry. How would you debug it?

Debug missing Application Insights telemetry from a .NET API

Investigate a .NET API that appears to run but sends little or no telemetry to Application Insights.

1Say itAnswer out loud first

2CompareCompare with Core answer

3RefineRefine with Stronger and Advanced

TL;DR

I would first decide what is missing: all telemetry, only logs, only dependencies, only traces, or a sampled subset. Then I would verify the Application Insights connection string, environment-specific configuration, SDK or OpenTelemetry setup, and whether the app is sending telemetry to the expected resource. I would check sampling and ingestion limits before assuming data is lost. If the issue started after deployment, I would compare telemetry configuration and package changes with the previous release.

Full answer below

Practice focus

Connection strings, SDK or OpenTelemetry configuration, sampling, ingestion failures, network restrictions, and telemetry pipeline checks.

Answer first

Answer path

Core answer first, then checkpoints toward a stronger answer.

Start
Core answer
Start here. This is the direct spoken answer to practice first.
Why this question matters
Missing telemetry can originate in instrumentation, configuration, sampling, network delivery, ingestion, workspace routing, or the query used to find it. First identifying which telemetry types and instances are absent narrows the broken stage.
I would first decide what is missing: all telemetry, only logs, only dependencies, only traces, or a sampled subset. Then I would verify the Application Insights connection string, environment-specific configuration, SDK or OpenTelemetry setup, and whether the app is sending telemetry to the expected resource. I would check sampling and ingestion limits before assuming data is lost. If the issue started after deployment, I would compare telemetry configuration and package changes with the previous release.
Checkpoint
Stronger answer
Optional upgrade with examples, trade-offs, and sharper phrasing.
I would trace the telemetry path from app to Azure Monitor ingestion. The app may generate telemetry but fail to send it because of network restrictions, Entra authentication settings, wrong endpoint, missing role, TLS issues, or SDK misconfiguration. It may also send correctly while the portal query, sampling, or workspace configuration makes data look incomplete. I would use SDK diagnostics, a controlled test event, live metrics where appropriate, and Azure Monitor health signals to narrow the missing step.
Finish
Advanced answer
Optional deeper angle for production judgment and nuance.
In production I would keep telemetry reliable enough to debug telemetry failures. That means monitoring ingestion health, recording deployment version and instance id, validating observability after release, and avoiding high-cardinality custom properties that drive cost or throttling. If I move from classic Application Insights SDK to OpenTelemetry, I would compare dashboards, alerts, sampling, and trace continuity in staging before switching production. The outcome is not just restored telemetry; it is confidence that incidents remain observable.

Review signals

Use these to catch weak phrasing, shallow reasoning, and risky claims.

Common mistakesCandidateCommon mistakesMistakes that weaken the answer or signal shallow understanding.Open details

Details

Assuming no portal data means the app produced no telemetry.
Ignoring sampling and ingestion limits.
Sending telemetry to the wrong Application Insights resource.
Changing observability libraries without validating existing alerts.

Red flagsCandidateRed flagsSignals that an interviewer may treat as risky.Open details

Details

Cannot describe the telemetry pipeline from app to Azure Monitor.
Has no way to send or identify a controlled test telemetry item.
Does not check connection string or environment-specific config.
Ignores sampling when counts look too low.

Follow-up prompts

Quick interviewer prompts inside this drill.

Follow-up questionsCandidateFollow-up questionsLikely next questions after the main answer.Open details

Details

Treat these as the next interviewer turn. Answer one out loud, then save the gap in your practice notes.

How would sampling make telemetry look missing?
What would you check after moving to OpenTelemetry?
How would you validate telemetry after deployment?

Continue the section

Next in Azure Production Incident Debugging Essentials: SQL Timeouts After Deploy

Step 15 of 15

Debug Azure SQL timeouts after a .NET API deployment

Opening drill

Debugging scenarioMedium~10 minAzure Production Incident Debugging Essentials / 14 of 15

Interview question

A production .NET API is running, but Application Insights shows missing or incomplete telemetry. How would you debug it?

Debug missing Application Insights telemetry from a .NET API

Investigate a .NET API that appears to run but sends little or no telemetry to Application Insights.

1Say itAnswer out loud first

2CompareCompare with Core answer

3RefineRefine with Stronger and Advanced

TL;DR

Full answer below

Practice focus

Connection strings, SDK or OpenTelemetry configuration, sampling, ingestion failures, network restrictions, and telemetry pipeline checks.

Answer first

Answer path

Core answer first, then checkpoints toward a stronger answer.

Start
Core answer
Start here. This is the direct spoken answer to practice first.
Why this question matters
Missing telemetry can originate in instrumentation, configuration, sampling, network delivery, ingestion, workspace routing, or the query used to find it. First identifying which telemetry types and instances are absent narrows the broken stage.
I would first decide what is missing: all telemetry, only logs, only dependencies, only traces, or a sampled subset. Then I would verify the Application Insights connection string, environment-specific configuration, SDK or OpenTelemetry setup, and whether the app is sending telemetry to the expected resource. I would check sampling and ingestion limits before assuming data is lost. If the issue started after deployment, I would compare telemetry configuration and package changes with the previous release.
Checkpoint
Stronger answer
Optional upgrade with examples, trade-offs, and sharper phrasing.
I would trace the telemetry path from app to Azure Monitor ingestion. The app may generate telemetry but fail to send it because of network restrictions, Entra authentication settings, wrong endpoint, missing role, TLS issues, or SDK misconfiguration. It may also send correctly while the portal query, sampling, or workspace configuration makes data look incomplete. I would use SDK diagnostics, a controlled test event, live metrics where appropriate, and Azure Monitor health signals to narrow the missing step.
Finish
Advanced answer
Optional deeper angle for production judgment and nuance.
In production I would keep telemetry reliable enough to debug telemetry failures. That means monitoring ingestion health, recording deployment version and instance id, validating observability after release, and avoiding high-cardinality custom properties that drive cost or throttling. If I move from classic Application Insights SDK to OpenTelemetry, I would compare dashboards, alerts, sampling, and trace continuity in staging before switching production. The outcome is not just restored telemetry; it is confidence that incidents remain observable.

Review signals

Use these to catch weak phrasing, shallow reasoning, and risky claims.

Common mistakesCandidateCommon mistakesMistakes that weaken the answer or signal shallow understanding.Open details

Details

Assuming no portal data means the app produced no telemetry.
Ignoring sampling and ingestion limits.
Sending telemetry to the wrong Application Insights resource.
Changing observability libraries without validating existing alerts.

Red flagsCandidateRed flagsSignals that an interviewer may treat as risky.Open details

Details

Cannot describe the telemetry pipeline from app to Azure Monitor.
Has no way to send or identify a controlled test telemetry item.
Does not check connection string or environment-specific config.
Ignores sampling when counts look too low.

Follow-up prompts

Quick interviewer prompts inside this drill.

Follow-up questionsCandidateFollow-up questionsLikely next questions after the main answer.Open details

Details

Treat these as the next interviewer turn. Answer one out loud, then save the gap in your practice notes.

How would sampling make telemetry look missing?
What would you check after moving to OpenTelemetry?
How would you validate telemetry after deployment?

Continue the section

Next in Azure Production Incident Debugging Essentials: SQL Timeouts After Deploy

Step 15 of 15

Debug Azure SQL timeouts after a .NET API deployment

A production .NET API is running, but Application Insights shows missing or incomplete telemetry. How would you debug it?

Practice focus

Answer path

Why this question matters

Review signals

Follow-up prompts

Continue the section

A production .NET API is running, but Application Insights shows missing or incomplete telemetry. How would you debug it?

Practice focus

Answer path

Why this question matters

Review signals

Follow-up prompts

Continue the section