Joseph Karl Crisostomo

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

Summary

Full-stack engineer who ships production Ruby on Rails SaaS — clean architecture, role-based auth, automated tests, and zero-downtime deploys. Comfortable across the stack with React/TypeScript and at home improving existing codebases.

Skills

• Backend: Ruby, Ruby on Rails, PostgreSQL, Node.js, REST integrations, Python, Django
• Frontend: React, TypeScript, Hotwire (Turbo/Stimulus), Next.js, Tailwind CSS, Leaflet
• Testing & Quality: Rails test suite, Minitest, Capybara, RuboCop, Brakeman, Playwright
• Infra & Tooling: AWS (EC2, S3, RDS, CloudWatch), Docker, Kamal, Git, Claude Code

Experience

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

On-site · Feb 2024 – March 2026

• Took a backend service from 0 to ~90% test coverage, improving overall maintainability and integrity of the system.
• Optimized slow database queries through in-depth inspection and root-cause analysis.
• Managed containerized (Docker) services deployed on an on-premise Linux server (Ubuntu) and on AWS, orchestrated with Elastic Kubernetes Service (EKS).
• Built an automated build pipeline with S3 (source), CodeBuild (containers), and ECR (images), and automated infrastructure provisioning with AWS CloudFormation.
• Integrated AWS RDS as the core database, ElastiCache (Redis) for caching, and Amazon MQ as a message broker; ran automated smoke and load testing with Grafana K6.

Web Developer (Intern) — Dashlabs.ai

Remote · Aug – Sept 2022

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

Selected Projects

Aqualytix — Production Rails SaaS (Water-Quality Monitoring)

Solo, full-stack · Deployed to production

• Built end-to-end in Ruby on Rails: domain model, role-based authorization, configurable per-station alerts with email notifications, and a reporting suite with server-side PDFs (Prawn).
• Shipped as seven independently deployable vertical slices; backed by model, controller, and mailer tests; deployed zero-downtime with Kamal/Docker on AWS EC2 with CloudWatch monitoring.

Kuryente Watch — Real-Time Community Web App

Solo, full-stack · infanta.kuryentewatch.app

• Rails 8 PWA with role-based access (Devise), live map updates via Action Cable, and Web Push notifications — no Redis dependency (Solid Queue/Cache/Cable).
• Security and quality gates with Brakeman, RuboCop, and bundler-audit; deployed via Kamal/Docker.

Education

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

2019 – 2023