Mastering KQL: The Art of Querying in Azure's Data Universe

In the vast constellation of Azure services, data flows like stardust—scattered across logs, metrics, traces, and telemetry. To make sense of it all, you need more than just a query language. You need a lens. A scalpel. A symphony conductor.

Enter Kusto Query Language (KQL)—a language built not just for querying, but for understanding. Whether you're chasing down elusive exceptions, monitoring performance bottlenecks, or decoding the heartbeat of your cloud infrastructure, KQL gives you the power to ask the right questions—and get answers fast.

This guide is your deep dive into the most essential and advanced KQL queries, including:

• 🧨 Exception and error detection
• ⚠️ Warning and informational log analysis
• 📊 Performance metrics and time-series insights
• 🔐 Security and audit trail queries
• 🧠 Advanced filtering, summarization, and pattern matching

Each query is a tool. Each pattern, a story. And each insight, a step closer to mastering the art of observability.

Absolutely, Durgesh! Here's a revised and expanded blog title along with a refined intro that reflects the broader scope of KQL queries—including exceptions, errors, warnings, info logs, performance metrics, and security insights.

🧨 Exception & Error Detection
exceptions
| where timestamp > ago(1d)
| summarize count() by type, method, outerType, bin(timestamp, 1h)

traces
| where severityLevel == 3  // Error
| summarize count() by message, bin(timestamp, 1h)

⚠️ Warning & Informational Logs

traces
| where severityLevel == 2  // Warning
| summarize count() by message, bin(timestamp, 1h)

traces
| where severityLevel == 1  // Information
| summarize count() by message, bin(timestamp, 1h)

📊 Performance Monitoring
Perf
| where ObjectName == "Processor" and CounterName == "% Processor Time"
| summarize avg(CounterValue) by bin(TimeGenerated, 5m), Computer

requests
| summarize avg(duration) by bin(timestamp, 5m), name

🔐 Security & Audit Insights

SecurityEvent

| where EventID == 4625
| summarize FailedLogins = count() by Account, bin(TimeGenerated, 1h)

SigninLogs
| where ResultType != 0
| summarize count() by UserPrincipalName, AppDisplayName, bin(TimeGenerated, 1h)

🧠 Advanced Filtering & Case Logic

traces
| extend severity = case(
    severityLevel == 3, "Error",
    severityLevel == 2, "Warning",
    severityLevel == 1, "Info",
    "Other")
| summarize count() by severity, bin(timestamp, 1h)

📌 Summary Table by Severity

traces
| summarize Errors = countif(severityLevel == 3),
            Warnings = countif(severityLevel == 2),
            InfoLogs = countif(severityLevel == 1)