Joel Barrón · Python | Django | React Native | Expo

About

Senior software engineer with 10 years of experience designing and delivering backend platforms and cross-platform applications for fintech, consumer, and public-sector products.

Strong background building APIs and services with Python and Django, combined with hands-on experience delivering mobile and web products using React, React Native, Expo, and Astro.

I specialize in building systems that scale predictably, with a strong focus on data modeling, SQL and ORM query optimization, background processing, and safe database migrations.

My work emphasizes reliability in production environments, including asynchronous workloads, resilient third-party integrations, and long-running processes that must remain stable under load.

Comfortable working end-to-end with product and engineering teams, from technical discovery and architecture decisions to production releases and long-term system evolution.

Expertise

Production-grade tooling across backend, frontend, cloud infrastructure, and engineering practices.

Backend (Python & Node.js)

Python Django Django REST Framework Django ORM (profiling & optimization) Celery Django Channels / WebSockets FastAPI Node.js AdonisJS Express.js Background jobs & schedulers API design & versioning Security fundamentals

Performance & Reliability

SQL query optimization Index strategy (PostgreSQL / SQL Server) N+1 detection & fixes Caching strategies (Redis) Async processing Retries with exponential backoff Timeouts & rate limiting Idempotent APIs Graceful degradation

Frontend & Mobile

React React Hooks Next.js Astro React Native Expo TypeScript Tailwind CSS Bootstrap State management (Zustand, Redux basics) TanStack Query

Cloud, Infrastructure & Data

AWS EC2 / ALB / Route 53 RDS S3 SES SNS Amplify Azure (App Services basics) Docker Docker Compose Kubernetes (fundamentals) Proxmox Coolify Dockploy PostgreSQL SQL Server MongoDB Redis

Integrations & APIs

Third-party API integrations Stripe API PayPal API OpenAI API Webhooks & event-driven flows

Engineering Practices & Tooling

Git GitFlow GitHub Actions (CI/CD) SonarQube Code reviews & mentoring Linters (ESLint, Flake8) Formatting (Prettier, Black) Jira / Agile workflows Documentation & technical RFCs

Experience

Employer-led engagements with clear client outcomes and platform impact.

Tata Consultancy Services

Full Stack Software Engineer for American Express Mexico · Apr 2026 — Present

Remote

Continuing engagement with American Express on internal financial platforms, focused on backend modernization, performance, and reliability for enterprise environments.

American Express México

Internal financial platforms & backend modernization

Apr 2026 — Present

Led zero-downtime database migrations on critical financial data, applying backward-compatible schema changes and phased rollouts across multiple environments.
Optimized high-traffic Django APIs through query refactoring, index tuning, and ORM-level improvements to meet enterprise SLAs under production load.
Refactored legacy components toward modular, service-oriented designs, reducing coupling and enabling parallel delivery across teams.
Built asynchronous processing pipelines with Celery and message queues to support long-running financial operations without blocking user workflows.
Hardened integrations with internal and third-party APIs using retries, timeouts, and idempotent request handling to prevent duplicate financial events.
Strengthened CI/CD pipelines, code quality gates, and security remediation workflows in regulated enterprise delivery environments.

PythonDjangoCeleryPostgreSQLREST APIsCI/CD

Nexion Solutions

Full Stack Software Engineer · Aug 2021 — Mar 2026

Argentina 🇦🇷 · Remote

Maintenance and continuous improvement of internal platforms; modernization efforts toward microservices; CI/CD and security-focused delivery.

View projects

American Express México

Internal financial platforms & backend modernization

Aug 2025 — Mar 2026

Led backend modernization efforts, migrating legacy platform components toward more modular and service-oriented architectures.
Designed and optimized high-traffic Django APIs, reducing response times through query refactoring, index tuning, and ORM-level optimizations.
Implemented asynchronous processing pipelines using Celery and message queues to handle long-running financial operations without blocking user flows.
Planned and executed safe database migrations for critical financial data, ensuring backward compatibility and zero-downtime deployments.
Built resilient integrations with third-party and internal APIs using retries with exponential backoff, timeouts, and idempotent request handling.
Collaborated closely with product, QA, and DevOps teams to stabilize mission-critical systems under peak load and regulatory constraints.
Contributed to CI/CD pipelines, code quality gates, and security remediation efforts in enterprise environments.

PythonDjango 3.2Django REST Framework 3.12CeleryRedisAdonisJSNode.jsSQL Server 2017GitHub ActionsSonarQube

American Express Argentina

Field operations & mobile enablement platform

Jun 2023 — Jul 2025

Developed and maintained a cross-platform mobile application used by 500+ field representatives for daily operations.
Designed backend services to support offline-first workflows, background sync, and eventual consistency in low-connectivity scenarios.
Optimized API performance and data access patterns to support geolocation tracking, media uploads, and real-time activity tagging.
Implemented asynchronous jobs for data processing, notifications, and scheduled operations using Celery.
Collaborated on production releases to App Store and Google Play, ensuring stability across frequent update cycles.

React Native 0.70+Expo SDK 48React 18TypeScriptDjangoDjango REST FrameworkDjango ChannelsCeleryPostgreSQL 15AWS EC2AWS RDSAWS Cognito

Grupo Boldt

Casino, betting & loyalty mobile platforms

Aug 2021 — May 2023

Worked on mobile applications for casino and betting platforms operating across multiple LATAM markets.
Contributed to systems handling high-concurrency workloads, peak traffic during major sporting events, and real-time user interactions.
Implemented backend integrations to support promotions, account management, and transactional workflows.
Focused on application stability, performance tuning, and secure authentication flows in regulated environments.
Collaborated on release processes and quality controls for production-grade mobile applications.

React Native 0.65Expo SDK 45React 16.13Django 3.2Django REST Framework 3.12AWS LambdaAWS CognitoPostgreSQLPytestJest

Kaizentec

Full Stack Software Engineer · May 2018 — Jul 2021

León, Guanajuato, MX 🇲🇽 · On-site

Delivered banking and ERP solutions with Django/React stacks, focusing on business modules, integrations, and maintainable delivery.

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Banco del Bajío

Banking platforms for biometric authentication and document management

2018 — 2021

Developed backend services for banking platforms using Java and Spring Boot, integrated with SQL Server databases.
Implemented biometric authentication workflows as part of secure user identification and access control systems.
Built document management and digital archive modules for regulated financial information.
Designed batch and asynchronous processes for massive account statement generation and data extraction.
Worked on data-heavy queries and reporting flows, optimizing SQL Server performance for large datasets.
Collaborated with multidisciplinary teams under strict security and compliance requirements.

JavaSpring BootSQL Server 2016REST APIsBiometric servicesBatch processing

Andanenes

ERP platform for manufacturing and operations

2018 — 2021

Developed and maintained a multi-module ERP system covering purchasing, HR, production, warehousing, scheduling, and invoicing.
Worked on the gradual decomposition of a legacy monolith into service-oriented and microservice-based components.
Implemented domain-focused services to isolate critical business workflows and reduce coupling.
Optimized data access and reporting for operational dashboards handling large transactional volumes.
Supported long-term system evolution over multiple years, balancing new features with legacy constraints.

Django 2.2Django REST Framework 3.10PostgreSQL 11DockerDocker ComposeService-oriented architecture

Mi Rentero

Office rental management and billing platform

2020 — 2021

Built backend services for office rental management, including contracts, invoicing, and tenant notifications.
Implemented asynchronous processes for invoice generation, email delivery, and payment reminders.
Integrated cloud storage and email services to ensure reliable document delivery and auditability.
Improved system reliability by isolating long-running billing tasks from user-facing workflows.
Supported production deployments and maintenance of a multi-tenant platform.

Django 2.2Django REST Framework 3.10PostgreSQL 11AWS S3AWS SESCeleryDocker

ACRUX (Célula de desarrollo tecnológico)

Full Stack Software Engineer · Jan 2017 — Apr 2018

León, Guanajuato, MX 🇲🇽 · On-site

Government accounting system with procurement, supplier management, inventory/cost modules, and budgeting.

View projects

Municipality of Tultitlán

Government accounting system

2017 — 2018

Built backend and frontend modules aligned with official regulations.
Worked on query optimization and production deployments.

React 15.6Java Spring Boot 1.5SQL Server 2016DevExpress.NET Core 2.0

Café Consultores

Backend Developer · Feb 2016 — Dec 2016

León, Guanajuato, MX 🇲🇽 · On-site

Built RESTful services and modern SPAs with PHP/Laravel and JS frameworks; real-time updates via WebSockets.

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Web systems and SPAs

2016

Developed scalable RESTful services and SPAs with dynamic forms and real-time updates.

PHP 7Laravel 5.3Angular 2React 15GitLAMP/LEMP

Personal and freelance projects

Personal builds focused on architecture, async processing, and product-quality delivery.

FinZenio

Personal finance platform that combines manual expense tracking with AI-powered bank statement extraction, classification, and adaptive financial insights.

PythonDjangoDjango REST FrameworkCeleryPostgreSQLRedisReact NativeExpoAWS

Details

Dudi Comics

Educational reading platform for children where a virtual pet evolves through reading activity, driving engagement, rewards, and personalization, with analytics and reporting for schools.

PythonDjangoDjango REST FrameworkPostgreSQLRedisReactReact NativeExpoAWS S3

Details

Rente

Airbnb-style parking rental marketplace with mobile-first booking flows, pre-reservations by date ranges, spot selection, and Stripe-powered payments, plus a web portal for merchants to manage listings and availability.

ReactReact NativeExpoTypeScriptDjangoDjango REST FrameworkPostgreSQLRedisCeleryStripe

Details

Mentalysis

Clinical pre-screening web platform based on DSM-5 that profiles patients using medical history and symptoms, then delivers adaptive questionnaires to support mental health professionals.

PythonDjangoDjango REST FrameworkPostgreSQLElasticsearchReact

Details

Libraries

Reusable backend libraries and internal tooling to accelerate delivery, reliability, and observability.

JB DRF AUTH

A reusable authentication foundation for Django REST Framework projects, focused on passwordless authentication, OTP workflows, and multi-profile user architectures.

PythonDjangoDjango REST FrameworkPostgreSQLRedisAWS SNS

Details

JB DRF AUTH authentication flow with OTP

JB DRF AUTH merchant portal for listings and availability

Architecture: A modular Django app designed to be installed across multiple projects, providing shared authentication logic while allowing each project to define and extend its own User and Profile models.

Key modules:

Passwordless authentication using one-time passwords (OTP)
SMS-based OTP delivery with pluggable providers (AWS SNS by default)
Multi-profile user support (one user, multiple profiles)
Soft-delete support via django-safedelete for auth-related models
Reusable domain logic decoupled from project-specific models
Extensible hooks for future DRF ViewSets and serializers


                  graph TD;
  Client[Client App] --> API[DRF API];
  API --> OTP[OTP Service];
  OTP --> SMS[SMS Provider (AWS SNS)];
  API --> User[User Model];
  User --> Profiles[User Profiles];
  API --> DB[(PostgreSQL)]

JB Expo Dev Kit

Production-oriented Expo/React Native toolkit that packages authentication lifecycle, app bootstrapping, forms, API/query patterns, and reusable UI primitives into a consistent foundation for shipping mobile products faster.

TypeScriptReact NativeExpoReact QueryAxiosGluestack UI

Details

JB Expo Dev Kit architecture layers: app shell, auth, data, and reusable UI modules

JB Expo Dev Kit developer experience: setup, shared states, and onboarding conventions

JB Expo Dev Kit integration flow from package install to incremental adoption

Architecture: Layered package architecture where each concern (boot, auth, data, forms, UI, and app-status) is isolated but composable, allowing teams to install only what they need while keeping conventions consistent across apps.

Key modules:

Session-aware auth guards with token refresh, logout hardening, and protected route patterns
App bootstrap providers for config loading, startup checks, and dependency wiring
Reusable form controls powered by schema validation and standardized error rendering
HTTP + TanStack Query adapters with consistent request state, retries, and cache policies
UI primitives and app-status helpers for loading, empty, error, and offline states


                  graph TD;
  App[Expo App] --> Boot[Boot Providers];
  Boot --> Auth[Auth Module];
  Boot --> Query[Query + HTTP Layer];
  App --> UI[UI Primitives];
  Query --> API[(Backend APIs)]

JB React Web Dev Kit

Composable React web toolkit for internal platforms and dashboards, providing reusable foundations for auth, app shell, configuration, forms, data grids, and API/query orchestration with production-ready conventions.

TypeScriptReactReact RouterTanStack QueryAxiosTailwind CSS

Details

React Web Dev Kit architecture across shell, auth, forms, data grid, and query layers

React Web Dev Kit UI patterns for forms, filters, table states, and backoffice screens

React Web Dev Kit delivery impact: speed, integration consistency, and maintainability

Architecture: Modular front-end architecture split into shell, auth, config, form, table, and data-access layers so teams can assemble robust web apps with clear boundaries and predictable behavior.

Key modules:

Role-aware authentication and route protection with reusable guard patterns
App shell and environment bootstrap helpers for deterministic startup
Form primitives and validation abstractions for complex back-office workflows
Data grid, filters, pagination, and column tooling for heavy CRUD interfaces
HTTP client and query-state conventions for consistent API integration and caching


                  graph TD;
  Shell[React App Shell] --> Auth[Auth + Route Guards];
  Shell --> Forms[Form Kit];
  Shell --> Grid[Data Grid Primitives];
  Shell --> Query[Query Layer];
  Query --> API[(Backend APIs)]

Contact

Open to senior backend/full-stack roles, advisory work, and long-term partnerships.

Let’s build reliable, high-performance systems

Share your product context, scale, and constraints—I'll respond with a clear plan of attack.

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Joel Barrón Senior Backend Engineer (Python & Django)

About

Expertise

Backend (Python & Node.js)

Performance & Reliability

Frontend & Mobile

Cloud, Infrastructure & Data

Integrations & APIs

Engineering Practices & Tooling

Experience

Tata Consultancy Services

Nexion Solutions

Kaizentec

ACRUX (Célula de desarrollo tecnológico)

Café Consultores

Personal and freelance projects

FinZenio

Dudi Comics

Rente

Mentalysis

Libraries

JB DRF AUTH

JB Expo Dev Kit

JB React Web Dev Kit

Brands

Contact

Let’s build reliable, high-performance systems