$10M Launch Saved: Fix PostgreSQL High CPU in Minutes
Learn how a single inefficient SQL query caused a 95% CPU spike on Azure PostgreSQL and how we fixed it in 30 minutes.
(The solution wasn’t scaling up the hardware. It was 1 line of bad SQL.)
When a managed database service like Azure Database for PostgreSQL spikes CPU this hard, most people don’t check connections first.
Here’s the key: High connections are a symptom, not the cause.
You see them because an underlying problem (the bad query) causes performance degradation, triggering the application’s retry logic to flood the connection pool.
The real, silent killer in most cases is a single, inefficient query.
That’s why we bypassed logs and went straight to the live active session list to find the culprit.
The Culprit: A single, inefficient SELECT query. It caused table-level locking and killed the performance of every other process on the shared environment.
The Checklist Mindset Playbook for Managing Sev-1 Cases
This includes:
A proven incident-handling mental model
How to think clearly under pressure
How to avoid panic debugging
Get 25+ practical SQL queries.
If you manage production systems, this playbook will change how you operate.
After resolving 950+ Sev-1 incidents for Fortune 100 customers at Microsoft, I rely on one checklist mindset that never fails and you can get it from here.
🚀 Discover the new PostgreSQL Health Report one SQL file to diagnose Sev-1 incidents in minutes and fix them fast!
Resolution: 30-Minute Root Cause Analysis (RCA) to 20% CPU.
1. We isolated the exact query causing the bottleneck.
2. Applied a single, optimized index.
3. The CPU dropped instantly from 95% to a stable 20%. Launch was saved.
The Takeaway for Every Database Engineer:
For critical systems, stop thinking about scaling hardware when performance drops.
Always check your query execution plans first. Optimizing one bad line of SQL is often 100 times cheaper and faster than scaling your entire Microsoft Azure environment.
What simple tuning fix has given you the biggest, fastest win in your career? Share your optimization over hardware story below!