Marcel Coelho
Verified Expert in Engineering
Full-stack Web Developer
Brasília - Federal District, Brazil
Toptal member since February 1, 2021
Marcel is a senior software engineer with over seven years of experience with TypeScript, React, Node.js, and their related technologies. He's currently looking for opportunities to be part of a product team. He's held various roles, including staff engineer, senior full-stack engineer, and senior front-end engineer. Marcel joined Toptal to find projects to work on in a small, metrics-focused, highly productive team to build great products.
Portfolio
Experience
- JavaScript - 8 years
- TypeScript - 6 years
- React - 6 years
- Node.js - 4 years
- Next.js - 4 years
- Artificial Intelligence (AI) - 3 years
- Prompt Engineering - 3 years
- Retrieval-augmented Generation (RAG) - 2 years
Preferred Environment
Visual Studio Code (VS Code), Google Workspace, Slack, Discord, MacOS
The most amazing...
...project I've built was an AI-based travel advisory product using OpenAI, LangChain, Next.js, Google Maps API, and a lot of embeddings/semantic search.
Work Experience
Lead Full-stack Engineer
Promptd
- Led a team of engineers to build the app from the ground up, creating a robust tool that enables collaboration on AI prompts, LLM performance observability at scale, and model fine-tuning.
- Oversaw deployments responsible for serving 100,000+ daily LLM calls through the prompt rendering API with sub-100ms latency and very low error rate.
- Spearheaded a research effort to understand the direction in which the AI prompting tool market is going.
Lead Full-stack Engineer
El Camino Travel
- Led a team of three engineers, overseeing the end-to-end development and delivery of a data extraction pipeline to process unstructured text using LLMs, word vector embeddings, and map data, transforming it into structured travel recommendations.
- Developed a retrieval engine combining retrieval-augmented generation (RAG), vector search, and PostgreSQL queries to surface precise recommendations for user queries.
- Engineered a query suggestion generator using contextual data and prompt engineering to produce ideal suggestions tailored to user needs.
Staff Engineer
Opensea
- Led the development of the new OpenSea Wallet using Next.js, TypeScript, and Tailwind, creating a user-friendly wallet for OpenSea and other Dapps.
- Made key improvements to the SSR infrastructure, reducing page sizes significantly and boosting load speeds by up to three seconds across millions of daily requests.
- Transitioned selected Next.js pages from SSR to Incremental Static Regeneration (ISR), improving the application's performance and scalability. This shift helped in handling high-traffic spikes and DDOS attack mitigations.
Senior Full-stack JavaScript Engineer
Contentfly
- Helped, as the first hired engineer after the CTO, shape the direction for both the front-end (AngularJS) and back-end (Node.js, Express, and PostgreSQL) apps by making sure they would scale well and be simple to maintain.
- Led a team of two other full-stack engineers to build both features for the core app and a spinoff product.
- Built and helped maintain the database infrastructure as it scaled from a few hundred thousand rows to billions.
Senior Front-end Engineer
Appen
- Developed the project architecture used in most new Appen front ends using React, Redux, and Sagas.
- Spearheaded the development of a component library written in TypeScript.
- Organized projects in a Flux architecture, using Redux as the source of truth and Redux-saga and its generators pointing to a Spring Boot REST back end.
- Implemented a hybrid approach using iframes and redirects to solve the challenge of keeping the old UI working along the new implementation since the JSPs (their old Java, Spring, and Stripes stack) and React apps usually render in different ways.
Senior Full-stack Engineer
Escolare
- Developed both the front end, using React and TypeScript, and the back end using Firebase Cloud Functions and Hasura GraphQL.
- Implemented a school-focused live-video chat feature using Node.js (with Socket.IO), mediasoup, and WebRTC.
- Deployed a container and component pattern with both Recompose and Hooks; as our GraphQL client, we choose Apollo.
- Designed most of the screens for the app (using Figma) as we didn’t have any designers on our team.
- Managed two junior engineers using scrum methodology; held 2-week sprints with a grooming and planning meeting at the start, daily stand-ups, and a retrospective meeting once in a while.
Front-end Engineer
Connect
- Developed both the Courses and Events modules for their native app using React Native. I also organized and implemented their Git into a feature branch and pull requests workflow.
- Implemented the container and component with Recompose and Formik. When I joined the project, they were not following any single design pattern.
- Implemented the GitFlow process to solve a big challenge when integrating code from over 20 developers working at the same time in the same app.
Front-end Engineer
Coopersystem
- Rewrote most of the code when I joined the project. The team was two weeks late in the delivery and the code was very messy. I used the Flux architecture with Redux Form for input management and Redux Thunk for side effects.
- Implemented continuous integration and delivery with Jenkins using Docker containers; it was the best deployment experience I've ever had.
- Achieved a great delivery cadence, deploying to production almost every week.
Freelance Developer
Freelance
- Developed a class booking system for a local yoga studio using AngularJS, Firebase, and Node.js.
- Built a restaurant order tracking and feedback system as a SaaS product for local restaurants using AngularJS, Firebase, Node.js, and hosted in Heroku.
- Constructed a landing page for an alternative toys company using WordPress and jQuery.
- Designed and developed a restaurant reward program usign Adobe XD, PHP 5, jQuery, and UIkit.
Experience
Bitcat
http://bitcat.rocksI led a team of engineers to conceptualize, build, and deliver the product.
CONTRIBUTIONS
• Designed and implemented prompt engineering to give the AI cat host its unique personality and voice.
• Architected and oversaw the creation of a custom Node.js-FFMPEG bridge for efficient audio management and merging processes.
• Built and managed the podcast generation pipeline, automating the process from fetching news articles to creating a polished podcast.
Anki-based Remembering Progressive Web App (PWA)
Slatus | Status Scheduler for Slack
I developed Slatus to automate my weekly status to match my routine. I decided to transform it into a product when a lot of my friends started using it too.
Skills
Libraries/APIs
React, Node.js, Redux Form, Formik, Redux-Saga, REST APIs, Stripe, Google Maps, Google Maps API, Stripe API, React Query, WebRTC, Socket.IO, jQuery, Facebook SDK
Tools
Create React App, Vitest, Firebase Authentication, AI Prompts, Git, Slack, Google Workspace, Figma, Expo, Sketch, Sequelize, Expo.io, Jenkins, Sonar, React Apollo, Google Analytics, Adobe Experience Design (XD), Jira
Languages
JavaScript, TypeScript, TypeScript 4, Sass, GraphQL, HTML, CSS, SQL, Java, PHP 5
Frameworks
Redux, React Native, Express.js, Next.js, Tailwind CSS, Jest, AngularJS, LangGraph
Platforms
Firebase, Docker, Visual Studio Code (VS Code), Linux, WordPress, Google Ads, Heroku, MacOS
Storage
NoSQL, MongoDB, Cloud Firestore, PostgreSQL, MySQL
Paradigms
Agile, Scrum, Kanban
Other
Web Development, Solution Architecture, Software Design, Tailwind UI, Embeddings from Language Models (ELMo), Authentication, Server-side Rendering (SSR), Prompt Engineering, Front-end, Back-end, Back-end Development, Version Control, Performance Optimization, Responsive Design, Discord, WebSockets, Full-stack, LangChain, Semantic Search, Google Cloud Functions, Retrieval-augmented Generation (RAG), Large Language Models (LLMs), Artificial Intelligence (AI), Sotrybook, CI/CD Pipelines, Mediasoup, OAuth, Ads, Firebase Cloud Functions, Memberful, Large Language Model Operations (LLMOps)
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