Joseph Karl Crisostomo

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

Summary

Full-stack software developer with professional experience building and maintaining production web applications across the JavaScript and Ruby on Rails stacks. I troubleshoot and resolve platform issues end-to-end, integrate third-party and AI APIs, and ship iteratively with tests and documentation. I work independently with minimal supervision, communicate clearly across async and cross-functional teams, and build daily with AI-assisted ("vibe coding") tools while owning the architecture myself. Comfortable on UTC+8 with daily overlap with US working hours.

Skills

Languages / Web: JavaScript, TypeScript, HTML, CSS, Ruby, Python, SQL
Frontend: React, Next.js, Hotwire (Turbo/Stimulus), Leaflet, HTMX
Backend: Node.js, Ruby on Rails (MVC), Django, REST API design & integration, WebSocket/SSE
Databases: PostgreSQL (production), query optimization
AI-assisted development: Claude Code, Claude Design ("vibe coding"); built an AI model deployment/serving platform
Cloud / Infra: AWS (EKS, RDS, S3, CloudFormation, CodeBuild, ECR, ElastiCache/Redis, Amazon MQ), Docker, Kamal, on-premise Linux (Ubuntu)
Testing / Tooling: Unit/integration testing, Playwright, Grafana K6, Git
Strengths: Independent and self-driven, technology-agnostic, fast learner, strong async communicator

Experience

Backend Developer — Department of Science and Technology, Advanced Science and Technology Institute (DOST-ASTI)

On-site · Feb 2024 – March 2026

Built and maintained production web services, owning issues end-to-end and resolving them through root-cause analysis with minimal supervision.
Initiated unit testing from 0 to ~90% code coverage, improving the maintainability and integrity of the system.
Integrated core data services behind REST APIs, including PostgreSQL-class relational databases (AWS RDS), Redis caching (ElastiCache), and Amazon MQ as a message broker.
Performed database query optimization through in-depth inspection and root-cause analysis.
Managed containerized (Docker) services and automated build pipelines (S3 → CodeBuild → ECR), enabling fast, repeatable deployments.
Ran automated smoke and load testing with Grafana K6.

Web Developer (Intern) — Dashlabs.ai

Remote · Aug 2022 – Sept 2022

Contributed to the maintenance of the platform's Patient Management Service.
Handled customer queries across multiple channels (email, chat), resolving issues with clear communication.

Projects

Aqualytix — Water-Quality Monitoring Platform (solo, end-to-end)

https://aqualytix.hackwithsef.xyz

Built and deployed a production monitoring platform for an industrial water district client, solo and end-to-end: product, architecture, full-stack code, database, infrastructure, and ops.
Stack: Ruby on Rails (MVC), PostgreSQL, Hotwire (Turbo/Stimulus) for client-side interactivity, server- and client-side JavaScript.
Delivered in 7 incremental, independently deployable phases, each demoable — shipping features iteratively with feedback loops.
Wrote a real test suite (model, controller, and mailer tests with fixtures and mailer previews) and maintained design/handover documentation.
Built role-based authorization, interactive trend charts, PDF reporting, and email alerting; deployed zero-downtime via Kamal/Docker on AWS with CloudWatch monitoring.
Developed using Claude Code as an AI pair-programmer while owning all architecture, data-modeling, and UX decisions.

AI-as-a-Service Platform (DOST-ASTI)

Designed and built a platform to standardize how AI/ML models are developed, deployed, and exposed as consumable APIs across institutes.
Standardized process cut AI-model integration from ~2–3 months to days.
Built with AI assistance but hand-written where it counts, sharpening core coding and architecture skills.

Kuryente Watch — Real-Time Community Status App

https://infanta.kuryentewatch.app

Crowdsourced, near real-time electricity-status web app (Rails 8 + Hotwire, PostgreSQL) with an interactive Leaflet map, Action Cable live updates, and Web Push notifications.
Built end-to-end with agentic AI ("vibe coding": Claude Code + Claude Design) with me acting as technical pilot/reviewer, catching when the AI veered off course thanks to hands-on coding experience.

Education

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

2019 – 2023