Profile Before You Optimize

You’re sure the database query is slow. You optimize it. Query time drops 50ms. But the request is still slow.

The bottleneck wasn’t the query. It was JSON serialization.

Get the real answer with profiling:

node --prof server.js
# Make requests...
node --prof-process isolate-*.log > profile.txt

Or use clinic.js for flame graphs:

clinic doctor -- node server.js

Or the Node.js inspector:

node --inspect server.js
# chrome://inspect

The thing you’re sure is slow usually isn’t. Find the actual bottleneck. Premature optimization wastes weeks for 2% gains.

Measure first. Optimize once. Ship faster.