Pay cheap, pay twice—or hire me and get it done right the first time. I’m a senior software engineer who excels at fixing the mess others leave behind. If your project’s in trouble, I’ll turn it around fast and right. I can help you with: ✓ Taking over, auditing, and improving your existing mobile app ✓ Creating your mobile app from scratch ✓ Joining your mobile team My strengths ✓+20 years of experience as a software engineer and architect ✓ +10 years of experience creating mobile apps ✓ Worked with companies of all sizes: startups, SMEs, and large corporations ✓ Business oriented. I’m an entrepreneur myself. ✓ Industry best practices (Test-Driven Development (TDD), Clean Architecture, Clean Code, SOLID principles, and CI/CD) ✓ Latest Android technologies (Kotlin, coroutines, MVVM, Jetpack Compose, JUnit, MockK) ✓ Experience with Flutter, Kotlin Multiplatform and many backend technologies. ✓ On the shoulders of AI. I harness AI-powered tools like GitHub Copilot, Cursor, and Windsurf to boost efficiency in development, automation, and problem-solving ✓ Willing to push the boundaries and assuming new challenges FAQ 1. Why should I trust you over other freelancers? I’ve been hired repeatedly to fix projects that were left in chaos by other developers. I bring proven experience in delivering quality code and rescuing troubled projects. 2. How do you handle poor-quality code from previous developers? I specialize in assessing and fixing messy code. Instead of starting from scratch, I analyze what can be salvaged and ensure the project gets back on track efficiently. 3. What if I’m not technical? Can you help me understand progress? Absolutely. I provide clear communication, regular demos, and updates to ensure you’re always in the loop, regardless of your technical background. 4. What happens if the project scope is unclear or changes? I’m used to working with evolving requirements, especially in fast-paced startups. I help refine the scope and keep the project aligned with your goals, even as they change. 5. Do you subcontract your work? No. When you hire me, you work directly with me. I don’t outsource or subcontract any part of your project. 6. Can you deliver high-quality work even if it’s more expensive? A higher rate reflects speed, expertise, and the ability to avoid common pitfalls. By leveraging AI tools and deep industry knowledge, I reduce technical debt, ensuring your project is not just built fast but built right—saving you time, money, and frustration down the road. 7. How will I know the project is progressing as planned? I provide regular progress updates and deliverables, ensuring transparency. You’ll always know what’s happening and why, with no surprises. 8. Why is it better to hire you than a cheaper developer? Cheaper developers often deliver poor results, costing you more in the long run. I fix those mistakes, delivering work right the first time to save you from expensive rebuilds. Technologies During my professional career I employed a number of technologies including C, C ++, Java, Kotlin, Flutter, Dart, PHP, Laravel, Python, SQL, .NET, Django, CSS, JavaScript, TypeScript, Angular, Spring Boot, computer vision, among others. More: cesarmauri.com I've worked with clients worldwide, both directly and through platforms like Malt and Shakers. Be among the first to hire me on Upwork! Let's talk?

Turning ideas into working products — fast. I help founders and startups launch AI-powered SaaS, web, and mobile apps in days, not months. ➤ Why Work With Me? ➥ Lightning-Fast MVP Delivery – Go from concept to clickable prototype by next week ➥ Product-Minded Developer – I think like a founder, not just a coder ➥ AI & Automation Expert – Build smart workflows with LLMs, agents, and generative tools ➥ Zero Busywork – Clean, scalable code with automated systems from day one ➥ Async-First Collaboration – Smooth workflow via GitHub, Slack, Notion (timezone-flexible) ➤ Tech Stack Snapshot Frontend: React • Next.js • Tailwind CSS • HTML5/CSS3 • Replit • Lovable.dev Backend: Node.js • Python • FastAPI • Flask • Supabase • Firebase AI & ML / GenAI: GPT-4 • LangChain • Whisper • DALL-E • OpenAI API • LLM Agents • Text-to-Image • Voice Agents • RAG • Machine Learning • Object Detection • OCR • YOLO • MLFlow Rapid Dev Tools: Cursor • Replit • Lovable • v0.dev • Bolt.new • Base44 ➤ Let’s Build Something Real , Fast Invite me to your job and let’s get your idea into users’ hands by next week. No fluff. Just shipped code. ✨ Bonus: I Speak Founder I don’t just code. I ask the right questions to shape your vision into a viable, technical reality. Whether it's an AI sidekick, no-code hybrid app, or scalable SaaS, I’ll help you build it lean, smart, and fast.

I build production-grade mobile and backend systems that scale. Over the past 5+ years I've gone from shipping cross-platform Flutter apps to architecting the full stack behind them, from real-time payment rails and biometric onboarding flows to high-volume reward engines processing 1.1M+ automated distributions for 300k+ participants. On the mobile side, I lead Flutter projects end-to-end. Clean Architecture, Riverpod/Redux state management, offline persistence, CI/CD with Codemagic, store deployments. I've also delivered multi-platform React Native/Expo apps with full iOS, Android and Web feature parity. On the backend side I work with NestJS microservices, Firebase Cloud Functions, Firestore and Docker. I've integrated payment ecosystems including ACH, SEPA, Wire and localized transfer methods across multiple regions. Security is something I take seriously too. Passkeys (WebAuthn), biometric liveness checks, JWT/OAuth flows, Soulbound Token reputation systems, the whole deal. A few things I've been core to shipping: • Volt Wallet, a crypto/DeFi wallet scaled to 50k+ users • Solid (solid.xyz), a multi-platform app with a global Visa debit card integration and a full crypto-to-fiat payment bridge • fuse_wallet_sdk, an open-source Dart package on pub.dev used by B2B partners • Flambu, a peer-to-peer rental marketplace with Algolia geosearch and real-time messaging • ShelfScan, an on-device OCR + Gemini-powered food and calorie scanner I'm comfortable owning a project from architecture through to deployment and I use AI-assisted workflows (Cursor, Claude, Gemini) to move fast without cutting corners on quality. If you're building something in fintech, Web3, or just need a senior mobile engineer who can handle the backend side too, let's talk.

I help SaaS founders and technical teams build, scale, and fix complex web applications—with a deep focus on payments, subscription billing, and database architecture. When payment webhooks break, database syncs fail, or subscription logic gets messy, it costs you direct revenue. With 18+ years of production software engineering experience, I step in as a hands-on architect to resolve technical bottlenecks, streamline billing workflows, and ensure your system runs without downtime. As the founder and lead engineer of Clever Certificates (a live production SaaS platform), I don't just write code—I operate SaaS. I manage the full product lifecycle: Next.js/Laravel backends, Supabase/Postgres schemas, Stripe billing, server-side analytics, and automated fulfillment. I bring that real-world operator mindset to every client project. --- 🛠️ Core Solutions I Deliver • Stripe & Subscription Architecture: Custom checkout flows, multi-tier billing, metered usage, webhook handlers, and fixing edge-case payment failures. • Supabase & Database Engineering: Schema design, Row Level Security (RLS) policies, database performance tuning, and bulletproof webhooks/syncing. • Full-Stack & API Development: Scalable backends and APIs built with Next.js, React, Laravel, Node.js, NestJS, and TypeScript. • System Reliability & Performance: Eliminating architectural debt, Core Web Vitals optimization, and Sentry error tracking. • Server-Side Analytics & AI: Meta Conversion API (CAPI), PostHog event tracking, GA4, and OpenAI API integrations. --- 💻 Primary Tech Stack Next.js • React • TypeScript • Laravel • PHP • Node.js • NestJS • Supabase • PostgreSQL • Stripe API • Vercel • AWS • PostHog • Sentry • OpenAI --- 📈 Proven Client Results ✔ Redesigned complex payment workflows to eliminate recurring billing failures. ✔ Improved Meta Purchase Event Match Quality to 9.0/10 using server-side tracking (CAPI). ✔ Stabilized a production SaaS platform serving 10,000+ active subscribers. ✔ Built zero-failure event-driven webhook pipelines for real-time payment state syncs. --- Whether you need a senior architect to lead a new product build, a specialized engineer to overhaul your Stripe setup, or an expert to fix production issues, let’s talk. Click "Invite to Job" or send a message to get started.

Staff Engineer & Architect | Hands-On Leader | React, Node.js, Java, Microservices Need an architect who doesn't just design systems but actually builds them? I'm Usman, and I'm not your typical engineering leader who's stepped away from the keyboard. Over 20 years, I've stayed hands-on—writing code, architecting systems, and leading teams at companies like Intuit, Carta, and Oracle. I believe the best leaders code alongside their teams. What Makes Me Different: 💻 Hands-On Technical Leader I don't just delegate—I architect, code, and deploy production systems myself Led microservices migration at Carta while personally implementing the core service extraction Built Intuit's API Orchestrator and contributed directly to critical components At DealCart, I architected AND helped build the entire ecosystem from consumer apps to warehouse management 🏗️ Architecture & Systems Expertise Successfully broke Carta's monolith into microservices (solved a 2-year problem in months) Designed Intuit's Webhook System processing 35-40 million events daily Expert in distributed systems, fault tolerance, and scalability Reduced MySpace IM load time from 15 seconds to under 3 seconds while cutting 60% of code 👥 Team Building & Mentorship Grew DealCart's engineering team from 1 to 20 engineers Founded mentorship program at Carta as Staff Engineer I code WITH my team, not just for them—leading by example My Technical Stack: Backend: Java, Node.js, Python, Spring Boot, Kafka, ActiveMQ, Microservices Frontend: React, Redux, HTML5, CSS3, JavaScript (I build UIs too) Cloud & DevOps: AWS, Jenkins, CI/CD pipelines Databases: MongoDB, Cassandra, SQL Server, Oracle Architecture: REST APIs, SOA, Distributed Systems, GraphQL Mobile: iOS (Objective-C, Swift), Android What I Can Do For You: ✅ Architect & Build - I design the system AND write production-ready code ✅ Rescue Legacy Systems - Modernize monoliths, fix performance issues, eliminate tech debt ✅ Scale Your Architecture - Build systems that handle millions of requests ✅ Mentorship & Code Reviews - Level up your team while delivering features ✅ Full-Stack Development - Backend services to React frontends—I do it all My Approach: I start by understanding your business goals, then I roll up my sleeves and build the solution. You get strategy AND execution from one person. Whether you need someone to architect your microservices migration or jump into your React codebase and ship features, I'm equally comfortable. Ready to work with a technical leader who actually codes? Let's discuss your project. I bring 20 years of experience, but I'm still shipping code every week.

As a driven entrepreneur with more than 15 years of experience in the technology sector, I have built and scaled multiple businesses from the ground up. I began my career working with global organizations such as Apple and Danone, where I developed strong foundations in operations, sales, and strategic planning. Later, I served as Regional General Manager at Rappi, helping launch and expand the company across Mexico, Argentina, Brazil, and several international markets, leading growth initiatives and partnerships in highly competitive environments. Together with my co-founders, I launched Isibit, a Latin American business travel platform that was accepted into the Y Combinator S20 batch in April 2020. When COVID disrupted the original model, I led the pivot toward Plerk, a fintech platform that delivered flexible benefits for global teams. As CEO and Co-CEO, I guided product development, go-to-market strategy, hiring, and fundraising. Plerk grew to more than 170 employees, raised over USD 12 million in funding, and was successfully acquired by Minu. I'm CEO and Co-Founder of Escal8, a Talent Intelligence platform that transforms how companies understand and develop their workforce. Using AI and conversational interfaces like WhatsApp, we help organizations move from gut-feel talent decisions to actionable, data-driven insights—covering recruitment, skills mapping, and personalized learning. Through Inveka, my Software Factory, I build digital products for clients worldwide. We specialize in rapid MVP development, scalable SaaS platforms, mobile applications, and AI-powered solutions. Our core services include: → Web & Mobile Development: iOS/Android apps, React/Next.js platforms, dashboards, and enterprise systems → Marketing Tech & Gamification: Interactive minigames, digital activations, and lead capture campaigns (built solutions for brands like Rappi, Dongfeng, and Rexona) → AI & Automation: Custom chatbots, document processing with AI, predictive maintenance systems, and intelligent assistants. → Tech Consulting: Software architecture, digital strategy, and staff augmentation Inveka by the numbers: 30+ solutions delivered, $700K+ USD in successful projects. Our tech stack includes React, Next.js, React Native, Supabase, and Vercel—chosen for speed, scalability, and cost-efficiency. What sets us apart: results-focused billing (we measure success by business impact, not hours logged), direct communication (you work directly with the builders), and a philosophy of "finding the how yes"—we don't take "no" for an answer; we find solutions. My expertise covers the full business lifecycle: transforming ideas into execution, turning services into productized revenue, recruiting high-performance teams, engaging regulators and enterprise stakeholders, and helping founders navigate from early-stage complexity to scalable operations. As part of the YC alumni network and the Latitud and 500 Global mentor community, I maintain active relationships with investors and operators across the region, which allows me to validate strategies quickly and support startups in securing funding and achieving measurable results.

10+ years experience in mobile and web full-stack development, I am the Swiss Army Knife of software development. I have expert knowledge in: - React / React-Native / Expo - NextJS / NodeJS - JavaScript / TypeScript - Google Firebase / Google Cloud Platform - MongoDB / PostgreSQL I regularly use the above stack in my day-to-day work, but I am also comfortable adapting to different tools that may be more suitable for a specific task. I am passionate about translating beautiful designs into efficient code to create exceptional user experiences. I am proficient in working across the entire web and mobile stack, focusing on writing testable code that follows the "Don't Repeat Yourself" principle. I also prioritize setting up automated pipelines for repetitive tasks. My approach is pragmatic, and I prefer integrating proven third-party software rather than reinventing solutions. I aim to release quickly and frequently, iterating until the customer is satisfied. I have experience working in diverse teams across various time zones, ranging from startups to large enterprises. I am solution-oriented and known to be the man for the hard and rough jobs. I work efficiently and take pride in delivering high-quality work on time.

Welcome to Dannenhauer Labs! Full Stack Developer | DevOps | Selenium Programming Languages: Java, Python, TypeScript, C#, PHP, GO, SQL Github Achievements: - Arctic Code Vault Contributor - Pair Extraordinaire - Pull Shark - Yolo Github Username: crypto-hippo Hi, I'm Dylan, a highly experienced Full Stack Developer with 6+ years of hands-on experience building scalable, maintainable web applications for clients across a wide range of industries. I specialize in crafting seamless user experiences on the frontend using React, Vue, Next.js, Nuxt.js and developing robust, secure backends with Java (Spring Boot), Python (Flask & FastAPI), and Node.js/Express. Currently diving into the Astro framework. I’ve helped businesses launch MVPs that generate revenue, revamp legacy systems, integrate third-party APIs, and build complex dashboards and SaaS platforms from the ground up. My work consistently emphasizes performance, clean code, and maintainability. Core Skills: Frontend: React, Vue, Next.js, Nuxt.js, TypeScript, Tailwind, Material UI, HTML5, SCSS Backend: Java (Spring Boot), Python (Flask, FastAPI), Node.js/Express, Astro, Next/Nuxt SSR DevOps: Docker, Kubernetes, Nginx, Apache, Linux System Admin Databases: PostgreSQL, MySQL, SQLServer, MongoDB, Firestore, Supabase, Firebase I'm Top Rated Plus on UpWork, with a track record of clear communication, on-time delivery, and client satisfaction. Whether you need a full-stack partner for a long-term project or a specialist to knock out specific features, I'm ready to help. My self-driven and self-taught approach to studying computer science is what made this dream possible. Web Scraping & Web Automation. In addition to full stack development, I have extensive experience in web scraping and web automation with Selenium. I’ve built dozens of high-performance tools for tasks like product monitoring, data extraction, and browser automation. One of my standout projects was a Windows application built in C#, Winforms, and Bunifu that launched parallel headless Chrome browsers to automate checkouts on Supreme New York, enabling users to secure limited-edition drops with speed and precision. My automation work spans a wide range of use cases, including crawling Amazon product listings, finding vehicles to flip on Craigslist, gathering market data on boats and funeral homes, as well as tracking competitor pricing in real time. Whether it’s navigating complex DOM structures, avoiding detection mechanisms, or designing tools for non-technical end users, my ability to automate the web efficiently and reliably is unmatched. Let’s build something great together! I am just getting warmed up so take advantage. Cheers, Dylan

I’m a Software Architect with 20+ years of experience designing and delivering complex, enterprise-grade systems that solve real-world business challenges at scale. I specialize in transforming highly complex processes into intelligent, automated, and scalable digital platforms — whether it’s a customer-facing web portal, a mission-critical backoffice system, or an AI-powered workflow engine. Over the years, I’ve worked across multiple industries, with deep domain expertise in: Building Supplies → Advanced rebate management systems, pricing logic, and distributor workflows Lease Management → End-to-end lease lifecycle systems, documentation automation, and compliance workflows Transportation & Logistics → Yard management systems, work order automation, and operational optimization I don’t just build software — I architect solutions to eliminate operational bottlenecks, reduce manual effort, and enable data-driven decision making. Core Expertise 🔹 Solution Architecture & System Design Designing scalable, maintainable, and high-performance architectures for complex business systems 🔹 Complex Workflow Automation Digitizing multi-layered business processes with rule engines, automation, and AI 🔹 Full Stack Development Laravel, Node.js, Angular, REST APIs — building robust end-to-end platforms 🔹 AI & Intelligent Systems AI agents, predictive analytics, and smart automation for modern enterprises 🔹 Enterprise System Modernization Transforming legacy systems into scalable, cloud-ready platforms What I Deliver ✔ Custom-built web portals and backoffice systems ✔ Automation-heavy platforms that reduce operational overhead ✔ Scalable architectures designed for long-term growth ✔ Clean, maintainable, and well-documented codebases ✔ Solutions tailored to complex, domain-specific challenges Selected Problem-Solving Experience Designed rebate management engines handling complex pricing and multi-tier distribution models Built lease management platforms covering contracts, approvals, renewals, and compliance workflows Developed yard and work order management systems optimizing logistics and operational efficiency Automated business-critical workflows, reducing manual intervention and human error significantly Why Clients Work With Me ⭐ 20+ years of hands-on experience in software architecture and development ⭐ Proven ability to solve complex, non-standard business problems ⭐ Strong understanding of enterprise operations and process optimization ⭐ Focus on long-term scalability, not short-term fixes ⭐ Clear communication and ownership from design to delivery Closing If you’re dealing with complex systems, messy workflows, or scaling challenges, I can help you turn them into structured, intelligent, and automated solutions. Let’s build systems that don’t just work — but work intelligently and scale effortlessly.

Looking for a senior full stack engineer who can ship fast, clean, and scalable solutions? I’m a vibe-driven software developer with 7+ years of experience building everything from 🚀 mobile apps in React Native to 🌐 full stack platforms in React + Node.js. I help businesses turn complex ideas into production-ready software that delights users and drives measurable growth. My focus is not just code — it’s creating systems that last, scale, and actually move the needle. ⸻ 🔹 Why Clients Choose Me 🧑‍💻 Full stack expertise – React Native, React, Node.js, TypeScript, SQL → seamless end-to-end delivery. ⚡ Performance-first mindset – scalable architecture, optimized queries, smooth UIs, and fast load times. ✨ Clean & maintainable code – modular, testable, and easy to onboard new devs. 🤝 Clear communication – proactive updates, transparent planning, and reliable collaboration. 🎯 Business impact – I care about outcomes: happier users, faster growth, lower tech debt. ⸻ 🔹 Services I Offer 📱 Mobile apps – React Native (Expo & bare workflow) 🌐 Web apps – React + Next.js, responsive & scalable 🔌 API development & integrations – REST, GraphQL, Auth, Stripe/payments 🗄️ Database design & optimization – PostgreSQL, MySQL, Firebase/Supabase ⚙️ Code audits & refactors – legacy cleanup, performance boosts 🔧 Ongoing support & scaling – CI/CD, testing, deployments ⸻ 🔹 Tech Stack React Native | React | Node.js | TypeScript | Next.js | SQL (Postgres/MySQL) | REST/GraphQL APIs | Redux/RTK | React Query | Firebase | Supabase | Stripe | Docker | CI/CD