Joseph Karl Crisostomo

joseph.dev.ph@gmail.com · +63 960 4431 908 · Manila, PH (UTC+8, overlaps US Eastern daily) · Portfolio Site

Summary

Full-stack engineer with strong Python, SQL, and PostgreSQL skills, focused on maintaining and improving production systems. I write and optimize SQL, validate large datasets, integrate APIs, and build with Claude Code while directing it — catching problems before they ship.

Skills

• Languages & Data: Python, SQL, PostgreSQL, Django, REST APIs
• AI-Assisted Development: Claude Code, Claude Design
• Backend & Integrations: Node.js, Ruby on Rails, WebSocket/SSE, REST integrations
• Frontend: React, TypeScript, Next.js, Turbo, HTMX
• Tooling & Infra: Git, Docker, AWS (RDS, S3, EKS, CloudWatch), Playwright

Experience

Backend Developer — Department of Science and Technology – Advanced Science and Technology Institute

On-site · Feb 2024 – Mar 2026

• Conducted database query optimization through in-depth inspection and root-cause analysis.
• Integrated AWS data storages: RDS as the core database, Elasticache (Redis) for caching, and Amazon MQ as a message broker.
• Managed containerized (Docker) services deployed to on-premise Linux (Ubuntu) and the cloud (AWS) — maintaining production applications.
• Initiated unit testing from 0 to roughly 90% code coverage, improving system maintainability and integrity.
• Built an automated build system using S3 for source storage, CodeBuild for builds, and Elastic Container Registry (ECR) for images; automated infrastructure provisioning with AWS CloudFormation.
• Performed automated smoke and load testing with Grafana K6.

Web Developer (Intern) — Dashlabs.ai

Remote · Aug – Sept 2022

• Contributed to maintaining the Patient Management Service of the platform.
• Handled customer queries across channels (email, chat).

Projects

Aqualytix — Production Water-Quality Monitoring Platform

Solo full-stack build · PostgreSQL · aqualytix.hackwithsef.xyz

• Built a production PostgreSQL platform that ingests station readings and flags anomalies against per-station thresholds — systematic data validation in practice.
• Directed Claude Code through the full build while owning architecture, data modeling, and trade-offs; raw coding background let me catch when the AI drifted.

Kuryente Watch — Real-Time Crowdsourced Status App

Solo full-stack build · PostgreSQL · infanta.kuryentewatch.app

• Shipped a live PostgreSQL + Rails PWA with real-time updates, built end-to-end with Claude Code under human direction.

Education

B.S. in Computer Science — Polytechnic University of the Philippines

2019 – 2023