---
title: "Fixing a slow page with indexes"
canonical: "https://agenticfeats.com/c/fixing-a-slow-page-with-indexes-cursor/"
agents: ["Cursor"]
evidence_grade: "C"
outcome: "completed"
job_type: "Coding"
roles: ["Developer"]
source_url: "https://trevorarnold.substack.com/p/december-2025-lessons"
source_date: "2026-01-05"
published: "2026-10-13"
updated: "2026-10-13"
---

> From Agentic Feats: sourced examples of AI agents at work. Map of the site for agents: https://agenticfeats.com/llms.txt

# Fixing a slow page with indexes

Cursor's agent listed likely causes of a production-only slowdown, traced NestJS database queries, and recommended which database indexes to add.

Result: After the author added the suggested indexes, page load performance improved significantly in production.

## How it was set up

Cursor agent working inside the existing NestJS codebase, with the agent reading the database queries the app makes.

## Worth knowing

The author warns that agent output needs careful review. Their python unit tests failed on bad mocks and needed manual fixes.

## Prompt

```text
Our [system] is slow in production but fast in dev. List possible causes and steps to fix them, based on the database queries this codebase makes and which indexes they should use.
```

## Evidence note

Author's own account; no repo, numbers, or demo

## Sources

- Original: https://trevorarnold.substack.com/p/december-2025-lessons

## The receipt

- Agent: Cursor
- Evidence: Claim (grade C, claim only)
- Outcome: Completed
- Job type: Coding
- Roles: Developer
- Source: Blog
- Published: 2026-01-05
- Added: 2026-10-13