I am a Senior Rails & DevOps Engineer with 15+ years of experience specialized in stabilizing, scaling, and modernizing complex web applications. When product owners and startup founders face messy codebases, performance bottlenecks, or tricky integrations, I step in to fix the root causes—not just apply temporary patches. I work 100% independently. No outsourcing, no middle-men. You get direct senior-level expertise. Here are the specific problems I solve for my clients: API / System Integration • Need to connect external services seamlessly? I integrate complex REST/OAuth2 APIs and third-party systems including Stripe, Mailchimp, FlightStats, Shopify, Simpro, Open-Meteo, Alpha Vantage, Google/Outlook Calendars, and Sendy. API Development • Need a custom, high-performance API? I build clean, well-structured, and secure APIs from scratch, thoroughly tested using Postman and curl, tailored for mobile apps or frontend consumption. Custom Shopify App Development • Need a tailored solution for your Shopify store? I build robust, non-embedded Shopify apps using Ruby on Rails to automate complex workflows and sync critical store data in real-time, including: - Products & Inventory: Real-time stock sync and automated catalog updates. - Orders & Fulfillment: Streamlined order processing, tracking updates, and custom fulfillment workflows. - Customers & Metafields: Advanced customer data management and extended store capabilities using custom metafields. - Automated PDF Generation: On-the-fly generation of custom invoices, packing slips, receipts, and downloadable business documents based on real-time store events. Performance & Scaling (Sidekiq, Redis, Queries) • Background jobs failing? Memory leaks? I analyze production logs, queue behavior, and server configs to eliminate bottlenecks and slash your server costs. Legacy Rails Modernization (v3.x to 7.x) • Stuck on an old Rails version? I dockerize your setup, resolve dependency hell, and modernize your stack for local development and production. Infrastructure & Cloud Migrations (Heroku / DigitalOcean / AWS) • Full server provisioning, Nginx configuration, SSL setup, Docker containerization, and automated deployment pipelines (Kamal, CI/CD). Bulletproof Stripe Integrations • Implementation and debugging of complex payment flows: Subscriptions, Webhooks, Payment Intents, and custom invoice handling. Modern Frontend & Fullstack Capabilities • Need UI modernization alongside backend fixes? I build fast, responsive, and interactive interfaces using Tailwind CSS, Vue.js, and Hotwire/Turbo, keeping your stack clean and efficient. Search Optimization • Transitioning slow database queries into lightning-fast searches using Elasticsearch and smart caching strategies. Let’s get your system stabilized. Reach out and briefly share your current tech stack and the challenges you're facing—I’ll take a look and let you know how we can fix it. Best regards, Sugi

I help businesses fix, stabilize, and scale complex web applications — Top Rated Plus, 100% Job Success, $100K+ earned across 6,889+ hours on Upwork. With 13+ years of experience in PHP (Symfony, Laravel), ERPNext/Frappe, Python, and DevOps, I specialize in taking over existing systems that need stability, performance, and long-term maintainability — the projects other developers find too messy or risky to touch. WHAT I DO BEST • Rescue & stabilize production apps — fix crashes, bugs, and broken deployments • Symfony & Laravel development, plus legacy upgrades (PHP 5→8, Symfony 2→6) • ERPNext / Frappe customization, integrations, and deployment • REST API development & third-party integrations • Performance tuning with Redis, Elasticsearch, and query optimization • DevOps: Docker, AWS, DigitalOcean, Linux, CI/CD, RabbitMQ queues & schedulers RESULTS I'VE DELIVERED • Upgraded large-scale Symfony apps to a modern, maintainable architecture • Resolved queue & worker failures in ERPNext after server migration • Cut response times using Redis caching and optimized Elasticsearch • Built and stabilized real-time systems (WebRTC) across web and iOS WHY CLIENTS KEEP ME LONG-TERM • I read and understand unfamiliar codebases fast • Clear, reliable communication and dependable delivery • Focused on stable, scalable solutions — not quick patches that break later BEST FIT FOR • Existing systems that need rescuing, improving, or scaling • Projects hitting performance or reliability limits • Ongoing development and long-term maintenance partnerships If you need a Symfony/Laravel expert, ERPNext consultant, API developer, or DevOps engineer who can step into a live system and make it solid — let's talk. Tech: PHP · Symfony · Laravel · Frappe/ERPNext · Python · Node.js · Angular · React · Vue · MySQL · Redis · Elasticsearch · Docker · AWS · DigitalOcean · REST API · WebRTC · RabbitMQ · CI/CD

Computer Scientist and Mathematician. I use Rust, Go, Python and Typescript. Research and R&D. Feel free to reach out if you need help with any of these points of interest.

⭐⭐⭐⭐⭐ Top Rated Plus | Engineering Manager | 13 Years Building Scalable Systems 👔 LEADERSHIP + AI DELIVERY Engineering Manager with 3+ years leading teams (10+ engineers) at Reliance Retail, backed by 10 years as Senior/Lead IC. I don't just write code—I align stakeholders, prioritize roadmaps, and deliver under pressure. ⚡ AI-AUGMENTED DEVELOPMENT I use OpenAI API, LLM integration, and AI agents to deliver 3x faster without sacrificing quality. Your project gets senior engineering judgment + AI velocity. 🛠️ TECHNICAL DEPTH • Backend: Python, Django/DRF, FastAPI, gRPC, Microservices, Celery • Data: PostgreSQL, MySQL, MongoDB, Redis, ElasticSearch • DevOps: Docker, Kubernetes, AWS/GCP, Linux/Nginx, CI/CD • AI/ML: OpenAI API, LLM Integration, AI Agent Development • Frontend: React, Redux, TypeScript 🎯 DOMAIN EXPERTISE • AgriTech: Built LivestockPro—farm management SaaS for 5-acre fish farm + 50 goats (inventory, expenses, profit analytics) • E-commerce: Backend systems at Reliance Retail & Clovia (search, recommendations, high-scale systems) • Industry 4.0: Led OT/IT connectivity for manufacturing IoT at Solulever (PLC/sensor integration) • Telecom: Led backend development for Wifog — virtual telecom platform in Sweden (core APIs, scalable backend systems) 🚀 ENGAGEMENT MODELS • Fractional Engineering Manager — Lead your team, set roadmap, deliver stability • AI-Augmented Development — Fast MVP builds, automation, AI integrations • Backend Architecture — Distributed systems, performance optimization ✅ Certified ScrumMaster® (CSM) | ✅ 100% Job Success | ✅ Long-term Partnerships 📞 Let's discuss how I can help you ship faster. 🔗 Portfolio: upendra.tech

— Among the Top 1% of Upwork Freelancers — Top Rated Plus Freelancer & Expert Vetted Freelancer With over 14 years of experience in software development, including the last 5 years as a CTO at licensed platforms, I bring a wealth of knowledge and expertise to each project. My passion lies in creating efficient, cost-effective solutions tailored to each business's unique requirements. I specialize in developing software that is both high-performing and low-resource intensive, and I'm always looking for opportunities to collaborate with clients on a long-term basis. I have extensive experience with GoLang, Node.js, JavaScript, ReactJS, PHP, Laravel, WordPress, MySQL, PostgreSQL, MongoDB, gRPC, Kafka, Redis, LESS, ElasticSearch, OpenAi, and ChatGPT. Additionally, I am well-versed in managing systems on Kubernetes, Docker, and Linux. With my riched experience, I bring a deep understanding of the unique challenges and requirements of different types of businesses, and I am well-equipped to help my clients scale their operations and achieve their goals. To help my clients get the most out of our collaboration, I offer a risk-free trial period. If you're looking for a skilled software architect and engineer with experience in the trading industry to help you scale your business with innovative IT solutions, please don't hesitate to reach out.

✔️ 𝗔𝘃𝗮𝗶𝗹𝗮𝗯𝗹𝗲 - I help startups and businesses build reliable backend systems, data platforms, and AI-powered automation solutions. Over the last 8+ years, I've worked across 𝗕𝗮𝗰𝗸𝗲𝗻𝗱 engineering, data engineering, and analytics -building systems that process millions of records, integrate with third-party APIs, automate business workflows, and deliver actionable insights. My experience includes designing scalable APIs, data pipelines, social media intelligence platforms, reporting systems, AI integrations, and cloud-native applications. What I can help you with ✔ Backend Development • FastAPI • Django / DRF • Flask • REST APIs • Microservices • Authentication & Authorization ✔ Data Engineering • ETL / ELT Pipelines • Airflow • PostgreSQL • MongoDB • Data Warehousing • Reporting Systems ✔ AI & Automation • OpenAI • Claude • LLM Integrations • AI Workflow Automation • RAG Pipelines • Agentic Systems ✔ Web Scraping & Data Collection • Scrapy • Selenium • Playwright • BeautifulSoup • Large-scale Data Extraction ✔ Cloud & DevOps • AWS (Lambda, ECS, EC2, RDS, S3, SQS) • Docker • Kubernetes • CI/CD ✔ Recent Projects • Built a Social Media Analytics Platform processing data from Reddit, TikTok, and Twitter to identify trends and influential accounts. • Developed AI-powered automation workflows integrating multiple APIs and LLMs for lead generation and business intelligence. • Designed data pipelines and reporting dashboards handling large-scale operational data and business KPIs. • Built backend systems supporting real-time data ingestion, processing, and analytics workloads. ✔ What Clients Appreciate • Strong communication • Ownership mindset • Clean, maintainable code • Fast turnaround • Ability to work independently If you're looking for someone who can take ownership of backend systems, data pipelines, or AI-powered workflows and deliver production-ready solutions, let's connect. Best regards, 𝗞𝗿𝗶𝘀𝗵𝗻𝗮

I help companies worldwide build, scale, and modernize enterprise-grade applications using .NET. With 11+ years of experience, I specialize in designing high-performance, secure, and scalable systems that support critical business operations. I’ve worked across industries including finance, healthcare, CRM, Inventory, ERP and e-learning—helping teams turn complex challenges into reliable, production-ready solutions. I bring deep expertise across the Microsoft ecosystem, with a strong focus on Blazor, ASP.NET Core, and modern full-stack architecture. What I do: Build scalable full-stack applications using C#, ASP.NET Core, and Web APIs Develop rich, interactive UIs with Blazor (Server & WebAssembly) Modernize legacy systems into clean, maintainable architectures Design systems using SOLID principles, CQRS, MediatR, and Domain-Driven Design Deploy and manage applications on Azure and AWS with CI/CD pipelines Ensure code quality through Test-Driven Development (xUnit, bUnit, Moq) How I add value: Improve system performance and scalability Reduce technical debt in legacy applications Deliver clean, maintainable, and future-ready solutions Align technology with real business goals I’m passionate about building systems that not only work—but scale, perform, and last. If you're looking to build or modernize a .NET-based system, or simply want to exchange ideas around scalable application architecture—feel free to connect.

🚀 The Top 3% of Node.js, AI & Backend Engineering Talent on Upwork 🤖 AI-Native Backend Development for Modern SaaS & Enterprise Products ⚡ 10+ Years of Professional Experience ⚡ AI Agents, Chatbots & LLM Integrations Delivered ⚡ Modern AI Stack: Cursor, Claude Code, GPT-4, Claude Sonnet & Copilot ⚡ 30–40% Faster Delivery Through AI-Assisted Engineering ⚡ Trusted by Startups, SaaS Companies & Enterprise Clients Welcome! 👋 I'm a Senior Node.js Developer, Node.js Backend Developer specializing in scalable, secure, and high-performance backend systems. For 10+ years, I've helped companies architect, build, optimize, and modernize SaaS platforms, enterprise applications, fintech products, healthcare solutions, CRM/ERP systems, and marketplace platforms. From Startup MVPs to enterprise ecosystems, I deliver software designed to scale with business growth. 🔥 WHAT YOU GET ✔ High-Performance Backend systems engineered to process millions of requests with 99.99% uptime. ✔ Production-ready features delivered 30–40% faster using AI-assisted development and AI-generated code workflows. ✔ End-to-End Development—from MVP Development and Product Development to long-term Backend Support and Application Maintenance. ✔ A Dedicated Developer and Technical Lead focused on measurable business outcomes. 🏆 RESULTS & IMPACT ✔ Delivered SaaS Development initiatives, ecommerce solutions, enterprise applications, and real-time systems serving thousands of users worldwide. ✔ Improved API performance by up to 50% through Backend Optimization, Redis caching, and Database Architecture improvements. ✔ Accelerated release cycles by 30–40% using AI-native engineering practices without sacrificing maintainability. ✔ Built Scalable Backend infrastructures capable of supporting millions of transactions and sustained business growth. 🚚 WHERE I DELIVER As a Senior Node.js Developer and Backend Engineer, I build REST API and GraphQL API ecosystems using Node.js, Express.js, NestJS, Fastify, Koa.js, JavaScript, TypeScript, WebSocket, Socket, Microservices, and Event-Driven Architecture. As an API Developer and REST API Developer, I deliver API Development, API Integration, Third-Party API Integration, Authentication, Authorization, JWT, OAuth, SSO, Swagger, OpenAPI, and API Documentation for secure enterprise environments. As a Full Stack Developer, I create Web Applications, Ecommerce Websites, Website Redesign projects, Browser Extensions, Google Chrome Extensions, Desktop Applications, Platform Plugins, Headless CMS, CMS Integration, Odoo Development solutions, and End-to-End Development initiatives. As an AI engineering partner, I help companies implement AI Development through AI Agent Development, AI App Development, AI Bots, Chatbots, ChatGPT Integration, OpenAI API integrations, OpenAI Codex Prompt workflows, AI Model Integration, and AI-generated code strategies that improve team productivity by 30–40%. 💳 INTEGRATIONS & AUTOMATION ✔ 10+ years integrating Stripe Integration, PayPal Integration, Twilio Integration, SendGrid, shipping providers, Payment Integration services, Webhooks, and System Integration workflows. ✔ Built asynchronous architectures using RabbitMQ, Kafka, BullMQ, Queue Management, and Message Queues to improve throughput and reliability. ✔ Automated Data Processing and ETL pipelines that reduce manual effort and support real-time decision-making. ⚒️ TECHNOLOGY ECOSYSTEM ✔ 10+ years of Backend Development using Node.js, Express.js, NestJS, Fastify, JavaScript, TypeScript, Python, PHP, Java, Kotlin, Scala, Ruby, C#, ASP.NET, Django, and modern Software Architecture practices. ✔ 8+ years delivering Full-Stack Development with React, Angular, AngularJS, Vue.js, HTML5, CSS3, Bootstrap, jQuery, Google Analytics, Adobe Photoshop, and Website Optimization strategies. ✔ 10+ years designing Database Development and Database Architecture solutions using MongoDB, PostgreSQL, MySQL, Redis, DynamoDB, Firebase, Supabase, Prisma, TypeORM, Sequelize, Mongoose, Microsoft SQL Server, MariaDB, Oracle, Neo4j, and Azure Cosmos DB. ✔ 7+ years deploying cloud-native applications with Amazon Web Services (AWS), Lambda, EC2, S3, Azure, Google Cloud Platform, Docker, Kubernetes, DevOps, Serverless Architecture, GitHub Actions, Jenkins, Git, and CI/CD pipelines. 🤖 AI-ASSISTED ENGINEERING STACK ✔ 5+ years leveraging Cursor, GitHub Copilot, Claude Code, OpenAI ChatGPT, GPT-4, and GPT-4o to accelerate prototyping, debugging, testing, and implementation by 30–40%. ✔ While AI accelerates delivery, critical architecture decisions, scalability planning, and Technical Lead responsibilities remain grounded in 10+ years of engineering experience. 🤝 LET'S BUILD SOMETHING GREAT Whether you need a Node.js Developer, Node.js Backend Developer, Backend Engineer, Full-Stack Developer, API specialist, AI integration partner or Technical Lead I'd be happy to discuss your architecture, roadmap, and next steps.

I started programming as a kid and it’s been more than 20 years now. My first language was Pascal, then C/C++ and then I moved on to interpreted languages, like PHP or Python. My professional career in web programming began back in 2011: since then I have delivered dozens of web applications in PHP (Symfony, Laravel) and Python (Django), among others. I treat my experience as a responsibility: I know what works and what doesn’t and I can judge the consequences of many technological choices - that’s why I am always honest and realistic with my clients, offer my advice, and if necessary, try to dissuade them from solutions that might not work as they have envisioned. My main focus is on code quality and practicality. My ambition is to write reliable, fast, easy-to-modify code that can be written in a relatively short time. I always seek a balance between perfection and practicality in my coding (since the road to perfection is infinite and time until the deadline is not). I am a strong proponent of code that can be documented only by its contents and unit tests. I am also a fast learner. I don’t treat any framework as anything more than another tool made for convenience. When the need arises, I can learn most programming libraries and frameworks on the spot (as long as it's in a programming language I know). I always enjoy a new challenge! My technical expertise covers: - Databases: PostgreSQL, MySQL, SQLite, Oracle, MongoDB - VCS: Git, SVN, Mercurial - Issue trackers: Jira, Asana, Redmine, Trello, Harvest - Hosting: AWS, Linode, CPANEL/WHM, GoDaddy, Github Pages - Server OSes and tools: GNU/Linux (experience with most of popular distributions), Kubernetes (minikube, EKS), AWS Lambda, Apache2, Nginx (php-fpm and uwsgi), Ansible - Code quality: PHPUnit, Python unittest (also in conjunction with Django), pytest - Search: ElasticSearch, Solr - REST API development: experience in Django (REST Framework), FastAPI, Symfony, Laravel, and Node.js - 3D graphics programming: OpenGL in JS WebGL, C/C++ OpenGL libraries and PyOpenGL+pygame in Python - Others: Websockets (experience with implementation in Django, FastApi, Python in Lambda, Laravel and Ratchet). - Payment gateway integration: Paypal, Stripe, Braintree, Przelewy24 My technology stack: Backend: - PHP: Laravel, Symfony - Python: Django, FastApi - JS: Node.js Frontend: HTML, JavaScript, TypeScript, React, Angular.io and Angular.js, Vue.js, jQuery, Three.js, CSS, SASS, LESS, Tailwind, Bootstrap, AdminLTE Mobile technologies: React Native If you are looking for a reliable business partner, I have good news for you: I work with Polcode Software House - one of the top rated agencies on Upwork, located in Poland (EU). We have achieved an impressive 98% Job Success rate (with over 700,000 hours logged!). We are a team of about 150 people (developers, account managers, project managers, and graphic designers) whose daily job is problem-solving. We never leave a customer with an unfinished project: working in a team we can guarantee the project's continuity, no matter what happens. We are here to help you have your work done and finished. Please visit Polcode's portfolio and check our feedback! Looking forward to our cooperation! Best regards, Maciej Zakrzewski Senior Full Stack Python Developer Polcode Dev Team

Senior Java Fullstack Developer with 6+ years of experience building scalable, cloud-native enterprise systems using Spring Boot, React, Angular, Microservices, and AWS. I specialize in: - Java/Spring Boot backend development & REST API design - Microservices architecture with Docker & Kubernetes - Cloud deployment on AWS (EC2, S3, Lambda, RDS) - Frontend development using React, Redux, Angular, TypeScript - Database optimization (PostgreSQL, MySQL, MsSQL, Oracle, Sybase, MongoDB, Apache Solr, Redis, Elasticsearch, DynamoDB) - Event-driven systems with Apache Kafka & RabbitMQ - CI/CD pipelines with Jenkins, Maven & Git Projects I've delivered include real-time analytics platforms, fintech payment systems, e-commerce backends, and enterprise SaaS applications — all built for high availability and performance at scale. Top Rated Plus on Upwork (Top 3%) | 100% Job Success | Toptal Qualified (Top 3% Global Talent) If you need a reliable Java developer to architect and deliver production-ready backend systems, let's connect.