Joseph Karl Crisostomo

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

Summary

Back-end engineer building production Rails on PostgreSQL, focused on clean data models and systems that hold up under load and across many clients. I work in a spec-driven, Claude Code-assisted workflow while owning the architecture and indexing decisions myself.

Skills

• Backend: Ruby, Ruby on Rails, PostgreSQL (JSONB), Redis (Elasticache), message brokers (Amazon MQ), REST/API design, data modeling, query optimization
• Scale & infra: AWS (EC2, RDS, S3, CloudWatch, SNS), Docker, Kubernetes (EKS), Kamal, load testing (Grafana k6), CI-grade automated testing
• AI-assisted dev: Claude Code (spec-driven), Claude API integration
• Frontend: Hotwire (Turbo/Stimulus), JavaScript, TypeScript, React

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 stores: RDS as core database, Elasticache (Redis) for caching, and Amazon MQ as a message broker for high-volume processing.
• Performed automated smoke and load testing with Grafana k6 to verify behavior under load.
• Initiated unit testing from 0 to ~90% coverage, improving maintainability and system integrity.
• Managed containerized (Docker) services across an on-premise Ubuntu server and AWS; orchestrated containers with Elastic Kubernetes Service (EKS).
• Built an automated build pipeline (S3, CodeBuild, ECR) and automated infrastructure provisioning with AWS CloudFormation.

Web Developer (Intern) — Dashlabs.ai

Remote · Aug – Sept 2022

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

Projects

Aqualytix — Production Rails + PostgreSQL Monitoring Platform

Solo, end-to-end · built with Claude Code · https://aqualytix.hackwithsef.xyz

• Designed and shipped a production Rails/PostgreSQL platform for a real water-district client, owning the full domain model (stations, readings, alerts, roles, settings).
• Delivered in 7 independently deployable vertical slices; documented architecture and data-model trade-offs to avoid future rework.
• Deployed via Kamal (zero-downtime) to AWS EC2 with CloudWatch metrics, alarms, and SNS alerting; backed by model, controller, and mailer tests.

Kuryente Watch — Real-Time Rails 8 + PostgreSQL App

Solo, end-to-end · built with Claude Code · https://infanta.kuryentewatch.app

• Real-time crowdsourced grid-status app: append-only event log fans out to live map updates and Web Push jobs.
• PostgreSQL with JSONB (geo boundary polygons), role-based access, and database-backed background jobs.
• Acted as technical pilot and reviewer, directing the AI and catching drift against the spec.

Education

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

2019 – 2023