Fullstack Developer & Tech Lead

Jesiel Pfeifer

I build and maintain production systems — from code to server. Specialized in TypeScript, React, NestJS and applied AI, with my own self-hosted infrastructure.

I am a Brazilian fullstack developer focused on shipping robust software: complex web platforms, integrations, AI agent automation and self-managed deployment environments.

View projects LinkedIn ↗ GitHub ↗
Production systems
5+
Years in the market
10+
Test coverage
80%

About me

Fullstack developer and tech lead experienced in production systems — complex web platforms, authentication, payments, integrations and messaging.

As tech lead in self-service banking solutions, I keep critical production applications running — root cause analysis, tracking the evolution of every release, and supporting L1/L2 and back-office teams. My domain spans C++ with CEN/XFS and ISO 8583 (ATM core) alongside a modern web stack (TypeScript, Node.js and React), unit testing with Jest and package delivery with Jenkins.

Beyond code, I design and operate my own infrastructure: a self-hosted homelab (Docker, Traefik, Cloudflare Tunnel, databases, media and dashboards), which gives me end-to-end visibility — architecture, deployment, monitoring and security.

I also apply AI in practical ways: autonomous agents that study tasks, implement code and run automated code review; website optimization for traditional search engines and for AI (SEO, GEO and AEO).

My work combines traditional software engineering with intelligent automation: CI/CD pipelines, automated testing, API integrations (payments, messaging, document issuance) and highly available environments. I have end-to-end experience — architecting, implementing, shipping and operating — which lets me deliver complete solutions and avoid integration issues between teams.

Beyond the technical side, I prioritize quality and security: reviewed code, protected data, predictable deploys and clear documentation. I believe production software must be simple to operate, easy to evolve and reliable day to day.

💰 Outcomes — Where I delivered value

Impactful deliveries in critical financial systems — availability, fraud prevention, quality and reliability of financial transaction processing.

🔄 More availability

Reduced application restarts caused by memory exhaustion, increasing availability of critical applications and avoiding interruptions in transaction processing.

🕵️ Fraud prevention

Implemented transaction monitoring focused on fraud prevention, with real-time visibility to detect suspicious patterns before they become losses.

🧪 Quality with AI

Raised automated test coverage from 10% to ~80% using an agentic development pipeline — fewer regressions, safer and more reliable deliveries.

📉 Fewer disputes

Reduced transaction dispute indicators by optimizing the financial transaction process, increasing end-to-end reliability.

Experience

10+ years in the market, 6+ of them in self-service banking solutions (ATMs), moving across operations, engineering and critical-system sustainment.

Tech Lead — Solutions Sustainment

Self-service banking

Feb 2023 – present · full-time

ISO 8583Oracle SQLLinuxSalesforceJira

  • Root cause analysis (RCA) on transactional network incidents, debugging ISO 8583 messages across the payment ecosystem.
  • Technical support for the transactional network, ensuring high availability of financial transaction processing.
  • Analyzed and traced ISO 8583 message flows between ATMs, POS terminals and backend systems.
  • Bridged operations and engineering — production incidents turned into actionable bug reports.

Technical Sustainment — ATM Software

Self-service banking

Jun 2021 – Feb 2023

  • RCA on production incidents with R&D for firmware and driver compatibility.
  • Python/Bash scripts to automate diagnostic routines.
  • Maintained firmware and device drivers for ATM hardware (C++/CEN-XFS).

Operations Analyst — ATM Fleet

Self-service banking

Jun 2020 – Jun 2021

  • Scheduled preventive, corrective and predictive maintenance for the ATM fleet.
  • Remote assistance and troubleshooting guidance to field technicians.
  • Python scripts to automate operational tasks and weekly availability reports.

Technical Support Analyst

Support & hardware

Jan 2014 – Mar 2020

  • B2B/B2C technical support for software and operating systems; hardware maintenance.

Stack & specialties

Projects

Production systems, open-source projects and my homelab infrastructure.

IAsConta — personal finance with AI

Open source

Financial management app with an integrated AI assistant — React, TypeScript and Node.js. Fully responsive interface for smartphone use.

Code on GitHub ↗

Self-hosted homelab — complete infrastructure

Infrastructure

Home server running Docker: Traefik reverse proxy, Cloudflare tunnels, ad-blocking DNS (Pi-hole), Tailscale VPN for secure remote access, media stack (Jellyfin, Radarr, Sonarr) and custom monitoring dashboards.

  • App deployment with automatic HTTPS via Cloudflare Tunnel
  • Infrastructure dashboard with metrics and AI usage stats
  • VPN with subnet routing and segmented firewall

AI agents — development automation

Automation

Autonomous development pipeline with AI agents: issue creation, technical code study, assisted implementation and automated code review on every pull request — with cost analysis across AI platforms.

  • Inline code review with claim verification against real code
  • AI token and credits usage dashboards
  • Cost comparisons for business decisions

SEO, GEO and AEO — visibility for humans and machines

Consulting

Audits and optimizations for traditional search (SEO), AI-powered search (GEO) — ChatGPT Search, Perplexity, AI Overviews — and direct answers (AEO): JSON-LD structured data, llms.txt, citable content and information architecture.

  • Schema.org (Person, FAQPage, WebSite, ItemList)
  • llms.txt and AI crawler preparation
  • Full technical audit: performance, indexing, accessibility

Academic projects and open source

GitHub

Public projects on GitHub: health scheduling system (VidaPlus), TypeScript authentication, software engineering with applied AI exercises and more — 22 public repositories ↗.

Frequently Asked Questions

Who is Jesiel Pfeifer?

Jesiel Pfeifer is a fullstack developer and tech lead with 10+ years in the market. He works on self-service banking solutions (ATMs) and production web platforms, with applied AI and self-hosted infrastructure. Graduated from UNINTER.

Does Jesiel Pfeifer work with ATMs and banking systems?

Yes. As a tech lead in self-service banking solutions, he keeps critical applications running: root cause analysis of incidents, L1/L2 and back-office support, tracing ISO 8583 messages between ATMs, POS terminals and backend, plus firmware/driver maintenance with C++/CEN-XFS.

Which stacks and protocols does Jesiel Pfeifer master?

Banking side: C++ with CEN/XFS and ISO 8583, Oracle SQL, Linux. Web side: TypeScript, React, Node.js, NestJS, Prisma, PostgreSQL, Redis, Docker and Tailwind. Also Python (automation), Jest (unit tests) and Jenkins (package delivery).

What were Jesiel's key results in production?

Reduced application restarts caused by memory leaks; transaction monitoring for fraud prevention; test coverage raised from 10% to ~80% with an agentic pipeline; and reduced transaction dispute indicators through financial process improvements.

Does Jesiel Pfeifer use AI in his daily workflow?

Yes. He uses AI-assisted development at work and runs a homelab managed by autonomous agents (Hermes) with OpenCode models. He also optimizes websites for both search engines and AI (SEO, GEO and AEO).

How can I hire Jesiel Pfeifer?

Through LinkedIn (linkedin.com/in/jesielpfeifer) or GitHub (github.com/JesielPfeifer). The contact section has the official links.

Contact

Available for opportunities as a fullstack developer, tech lead and projects with applied AI.

LinkedIn ↗ GitHub ↗