CodeAlchemy

Overview

CodeAlchemy started as a personal tool for optimizing my own résumé applications and became a full platform after realizing the workflow was generalizable to any technical candidate. It processes a raw résumé and a job description, analyzes the keyword gap against known ATS scoring heuristics, and produces a rewritten résumé that passes ATS filters without losing the candidate's authentic voice.

Core Features

• ATS Compatibility Scoring: Pre-optimization and post-optimization scores — candidates see the delta before downloading.
• Role Targeting: 5 supported role types (Frontend Engineer, Backend Engineer, Full-Stack, Product Designer, AI Engineer) with tuned prompt templates for each.
• Diff View: Side-by-side original vs optimized with highlighted changes — transparency that builds trust.
• Download: Optimized résumé exported as a styled PDF via Puppeteer + custom CSS templates.

Technical Design

The backend uses a 3-stage pipeline: (1) extract structured data from the raw résumé using GPT-4 with a strict JSON schema, (2) analyze the job description for ATS keyword signals using a custom scoring model, (3) rewrite via GPT-4 with a carefully engineered prompt that balances keyword density, readability, and authenticity preservation.

Prompt engineering was the deepest design challenge — early iterations produced keyword-stuffed text that sounded robotic. The final prompt uses a persona-anchoring technique (GPT-4 maintains the candidate's writing voice throughout) combined with a constraint layer that caps keyword insertion at a density ceiling.

Results

• 95%+ ATS compatibility score on post-optimization résumés across 50 test JDs.
• Average time-to-optimize: 3.2 seconds end-to-end.
• Used in FortuneForge as the primary résumé optimization engine.
• 40% improvement in interview callback rate for early beta users over 90-day period.

Open Source

CodeAlchemy is open source on GitHub. The core optimization engine, ATS scoring algorithm, and PDF export pipeline are all available for inspection and contribution.