🚀 SQL Server Performance Quirk I Ran Into
Recently, I noticed something odd in one of my stored procedures:
First run after SQL Server restart → 33 seconds ⏳
Subsequent runs → ~230 ms ⚡
At first glance, it looked like my indexing wasn’t working. But digging deeper, I realized this was a cold cache vs. warm cache issue:
On the first run, SQL Server has to compile the execution plan, load data pages from disk, and initialize tempdb structures.
On later runs, the plan cache and buffer pool are already primed, so queries fly.
âś… The Solution
Pre‑warm cache: Run critical procedures once after restart (via SQL Agent job) so the plan and data are ready before real users hit them.
Keep statistics fresh: Enable auto‑update (and async) or schedule jobs to refresh statistics. This ensures the optimizer has an accurate “map” of the data and picks efficient plans.
⚖️ Trade‑offs
Pre‑warming consumes memory up front, so only do it for high‑impact procedures.
Updating statistics too often can be I/O heavy, but too rarely leads to poor query plans. Balance is key.
💡 Takeaway: Sometimes performance issues aren’t about “bad queries” — they’re about how SQL Server warms up and how well its optimizer understands your data.
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