Available for new projects
Cássio Maletich
Senior Full-Stack Engineer
Ruby on Rails
React
JavaScript
Scalable Systems
I build production systems that handle real users, real money, and real scale.
From e-commerce engines to native apps and AI-driven automation, I focus on performance, maintainability, and business impact.
What I Do
Full-Stack, End-to-End
Deep expertise across the entire stack — from database architecture to polished UIs and cloud infrastructure.
Backend Engineering — Ruby on Rails
- Architect scalable Rails applications
- Payment systems & subscription logic
- API integrations (Amazon SP-API, DocuSign, Shopify, AI Vendors…)
- API Architecture & Design
- AI-driven systems
- High test coverage (RSpec / TDD mindset)
Frontend & Product — React / JavaScript
- Production-grade React & React Native apps
- Clean state management & component architecture
- Performance optimization
- UX focused on conversion
- Product catalog & checkout flows
Systems & Infrastructure
- AWS deployments
- CI/CD pipelines
- Background workers & job orchestration
- Large concurrent user bases
- Background jobs (Sidekiq), Redis, concurrency
- Gradual legacy migrations without downtime
Selected Impact
Results That Ship
A sample of real-world outcomes across different domains and scales.
Found and fixed hidden checkout tax duplication in a Spree-based e-commerce flow, improving trust and revenue
accuracy.
Identified and resolved a race condition causing duplicate shipment records during checkout — traced parallel
service
calls, implemented idempotency safeguards, and restored order integrity.
Led AI-powered scraping & document intelligence platform for investors: automated data extraction,
classification, and
dashboard insights from unstructured financial documents.
Built a native app MVP in 45 days after previous vendor failure — mastered React Native on the fly and delivered
production-ready.
Developed a subscription gifting system integrated in the previous flow serving 30k+ concurrent Shopify
users.
Led migration from Amazon Marketplace API to Selling Partner API, preserving compliance and adapting features.
How I Work & What's Next
Engineering with Intention
How I Work
- Business-first engineering
- Clean, pragmatic architecture
- Test-driven where it matters
- Advanced root-cause analysis skills
- Bias for shipping
- Calm under production pressure
Currently Interested In
- High-scale Rails systems
- E-commerce infrastructure
- AI-Driven Platform Architecture
- AI-assisted automation
- Complex backend challenges
Let's build something that impacts.
Open to challenging projects, consulting, and senior engineering roles.