I caused six wait types on purpose, one at a time, and measured each one for a single session. What each is blamed for, what it actually means, and the numbers it produced on SQL Server 2025. Wait types are the most misread figures in the product.
When a GUID Clustered Primary Key Gets Expensive
A GUID primary key can be useful. Learn when a GUID clustered primary key gets expensive, from page splits to index size, and when a bigint key can help.
SQL Server Network Latency: When the Database Isn’t the Slow Part
SQL Server network latency can make a fast database look slow. An application that fetches 4,000 orders one query at a time pays for every round trip. I measured the loop against one query, tested what ASYNC_NETWORK_IO means, and show how to check your own round trip time.
Outdated Statistics in SQL Server: The Optimizer Is Planning for Last Year
Outdated statistics in SQL Server can slow a query even when its code has not changed. On SQL Server 2025 with the legacy estimator, a stale statistic sent one join to 120,043 logical reads, and a targeted update brought it down to 18,220. Auto update helps, but it waits for a threshold, it samples, and it knows nothing about the rows that arrived today.
Your Index Rebuild Maintenance Plan Is Rebuilding Indexes Nobody Uses
Your index rebuild maintenance plan takes four hours every Sunday, fills the log and delays the backup. It may be buying you far less than everybody assumes.
AI Execution Plan Analysis: I Gave It My Plan and Asked What Was Wrong
I handed AI a plan with no warnings and healthy numbers, yet it read five million rows to return seventeen. That is the real test of AI execution plan analysis.
NOLOCK: Why It Counts Some Rows Twice and Misses Others
Everybody knows NOLOCK can show uncommitted data. Far fewer know why it counts some rows twice and misses others, with nothing rolled back. Let me show you.