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Brian Díaz
Verified Expert in Engineering
Software Engineering Developer
Santiago, Dominican Republic
Toptal member since September 8, 2022
Bio
Brian is an innovative developer and a problem solver. He has 11+ years of experience developing web back- and front-end services in various domains and with diverse tech stacks for startups and medium, and large companies. Experienced in working with fast-moving teams and under fixed deadlines, Brian is proficient in various methodologies and technologies, enabling him to learn quickly and adapt to new work environments.
Portfolio
ReClaim Tax Advisors
TypeScript, PostgreSQL, Supabase, Stripe, REST API Architecture, React, Node.js...
Saleo Inc.
React, TypeScript, HTML, CSS, JavaScript, Amazon Web Services (AWS)...
Zetta, LLC.
JavaScript, CSS, Python, React, Node.js, Full-stack Development...
Experience
- JavaScript - 11 years
- Software Engineering - 11 years
- Node.js - 11 years
- SQL - 9 years
- React - 8 years
- NestJS - 7 years
- TypeScript - 7 years
- NoSQL - 7 years
Preferred Environment
Slack, MacOS, Linux
The most amazing...
...project I've joined as one of the 1st engineers was involved in creating one of the top automotive startups in Brazil, which raised more than $55 million.
Work Experience
Senior Full-stack Engineer
2026 - 2026
ReClaim Tax Advisors
- Replaced a manual, attorney-driven filing process with one automated pipeline that carries a claim from intake and payment through PDF generation, e-signature, and delivery of a single downloadable, signed filing package.
- Delivered a tax refund claim platform end-to-end on TanStack Start, React 19, TypeScript, Supabase Postgres, and Cloudflare Workers, carrying it from architecture spec to a demo-ready product in under two months.
- Automated IRS Form 8821 and Form 843 preparation with pdf-lib, generating attorney-signed filing packages per business entity and adding a bulk ZIP export that replaced document-by-document manual downloads.
- Integrated Stripe checkout and webhooks, SignWell e-signature with verified webhooks, Postmark transactional email, and Google Places address autocomplete into a single automated claim lifecycle.
- Encrypted SSN and EIN at rest with last three digit lookups, added an append-only audit trail over document and claim mutations, enforced submission rate limits, and scaled intake to 50 business entities per client.
- Designed the PostgreSQL data layer and its role-based access model for clients, partners, and admins, and closed a critical unauthenticated data retrieval finding raised by an external security scan.
- Built a spreadsheet ingestion pipeline that loads claim CSVs through one idempotent import routine, with automated eligibility classification, refund quarter parsing, and form type routing, covered by unit tests.
Technologies: TypeScript, PostgreSQL, Supabase, Stripe, REST API Architecture, React, Node.js, Webhooks, Row-level Security (RLS), Lovable, Vite, Tailwind CSS, Zod, pdf-lib, PDF.js, RPC, TanStack Router, Bun, Personally Identifiable Information (PII)
Senior Full-stack Engineer
2025 - 2026
Saleo Inc.
- Led end-to-end development across Saleo’s SaaS platform and Chrome extension; built demo automation features, CRM integrations, analytics, and platform services using React, TypeScript, Node.js, AWS, PostgreSQL, DynamoDB, and browser extension APIs.
- Built an end-to-end demo navigation system with progress tracking, CTAs, branding, analytics events, and back-end CRUD across portal, viewer, and extension. Stack: React, TypeScript, Node.js, PostgreSQL, DynamoDB, AWS.
- Delivered Salesforce integration with OAuth, field mapping, influenced revenue analytics, and back-end lambdas for CRM attribution. Stack: React, TypeScript, Node.js, AWS Lambda, PostgreSQL.
- Built image discovery and replacement tooling inside the Chrome extension, including iframe/Shadow DOM scanning and asset import flows. Stack: TypeScript, React, Chrome Extension APIs.
- Built a webhook-driven Zapier integration to automate workflows from demo events, including subscription management and trigger services. Stack: React, TypeScript, Node.js, DynamoDB, AWS Lambda.
- Integrated session replay and heatmap analytics across the portal and extension with consent management and event instrumentation. Stack: React, TypeScript, Clarity SDK, CookieYes.
- Implemented cookie consent management across the SaaS portal and browser extension, including revisit controls and tracking hooks. Stack: React, TypeScript, CookieYes SDK.
- Removed legacy Workato integration, deprecated supporting proto implementations, and simplified integration UX and access controls. Stack: React, TypeScript, Node.js.
- Redesigned portal navigation system, user menu interactions, and shared sidebar UX patterns. Stack: React, TypeScript, design system.
Technologies: React, TypeScript, HTML, CSS, JavaScript, Amazon Web Services (AWS), Amazon S3 (AWS S3), AWS CloudFormation, Chrome Extensions, Vue, Angular, DOM, GraphQL, AWS Lambda, Terraform, Linaria, AWS SDK, PostgreSQL, Amazon DynamoDB, Redis, gRPC, RPC, TypeORM, OpenAI API, Jest, Tailwind CSS, Vite, Monaco, LaunchDarkly, Storybook, Playwright, Node.js, Software Engineering, Agile Software Development, Dashboards, REST API Architecture, Supabase, OAuth
Senior Full-stack Software Engineer
2024 - 2026
Zetta, LLC.
- Led the architecture and development of a scalable minimum viable product (MVP) in a fast-paced startup environment, ensuring the platform met early-stage business needs and allowed for iterative improvements.
- Developed a user management system supporting role-based access control (RBAC), empowering administrators and team owners to invite users, assign roles, and manage permissions.
- Integrated automated billing using Stripe, creating a system that supported both flat-rate and per-user fees, as well as volume-based pricing for data analytics services.
- Implemented a chat assistant using @nlux/react and @nlux/langchain-react, enabling interactive and automated user support within the platform.
- Defined the database schema to support user roles, permissions, teams, settings, and dashboard visibility, ensuring secure and efficient access to data for B2B clients.
Technologies: JavaScript, CSS, Python, React, Node.js, Full-stack Development, Single Sign-on (SSO), Google Cloud Platform (GCP), Tailwind UI, Tailwind CSS, TypeScript, Next.js, Vercel, Stripe, Stripe API, PostgreSQL, Tableau, Prisma, Docker, Minimum Viable Product (MVP), LangChain, Front-end, SQL, OpenAI API, RESTFul APIs, Responsive Web Design (RWD), Software Engineering, Agile Software Development, Dashboards, REST API Architecture, Supabase, OAuth
Senior Full-stack Engineer
2024 - 2025
Softrip LLC
- Led the end-to-end development of two full-stack modules—Travel Docs and Library Services—delivering scalable back-end APIs with Node.js/Express and fully responsive front-end interfaces using React, TypeScript, and Material UI.
- Translated Figma designs into pixel-perfect, responsive React components, including complex PDF-matching UIs for travel documentation, ensuring a seamless user experience across devices.
- Optimized database queries and application performance using PostgreSQL and Prisma, resulting in faster load times and reduced server resource usage across multiple endpoints.
- Achieved 100% unit test coverage for all new features and critical flows using Jest and React Testing Library, reinforcing reliability and reducing regression risk during deployments.
- Refactored legacy components into reusable modules, integrated Storybook for consistent UI documentation, and improved maintainability across the multi-tenant platform.
Technologies: React, Node.js, TypeScript, JavaScript, PostgreSQL, Git, Prisma, HTML, CSS, Material UI, Next.js, Vite, Amazon S3 (AWS S3), Amazon CloudFront, Express.js, Multitenancy, Storybook, Software Engineering, Redis, Agile Software Development, Dashboards, REST API Architecture, Supabase, Booking Systems, OAuth
Senior Software Engineer | Content Creator
2023 - 2024
Veracode Inc.
- Created Node.js Express Rest APIs for OWASP API Security Top 10 Course.
- Implemented security measures outlined in the OWASP API Security Top 10 guidelines. Implemented JWT, Rate Limiters, XSS, and SQL injection security measures, among others.
- Impressed the client with the efficiency with which these functional APIs were developed, recognizing their potential impact on the broader software engineering community.
Technologies: Node.js, OWASP, REST APIs, Express.js, MongoDB, SQLite, JSON Web Tokens (JWT), XSS Protection, SQL Injection Protection, Security, JavaScript, RESTFul APIs, Software Engineering, Agile Software Development, REST API Architecture
Software Engineer
2022 - 2023
TheoremOne
- Worked as a full-stack engineer, collaborating with clients in the US to deliver high-quality solutions.
- Developed new features, resolved bugs, and provided ongoing maintenance for a calendar application used by a prominent TV show company in the US. Technologies utilized include React, Node.js, JavaScript, Firebase, Jest, and CircleCI.
- Designed and implemented a secure service for sharing 3D printing resources for a medium-sized client in the US. Technologies employed include Node.js, TypeScript, NestJS, Google Cloud Platform (GCP), and JSON Web Tokens (JWT).
- Played a vital role in the Houston team, creating a minimum viable product (MVP) for ClarityFirst, a large US-based company. Developed the application using React, TypeScript, React Query, MUI (Material UI), React Testing Library, and Lexical.
- Led the front-end development for a major dental industry client, creating and implementing solutions using React, TypeScript, Material UI, Storybook, and React Query while transforming Figma designs into functional, responsive features.
Technologies: React, JavaScript, TypeScript, Node.js, Google Cloud Platform (GCP), Azure, Material UI, Material Design, Figma, Firebase, Jest, Storybook, React Query, REST APIs, NestJS, User Interface (UI), ECMAScript (ES6), Styled-components, React Redux, CSS, CSS3, jQuery, UI Components, Front-end, SQL, OpenAI API, RESTFul APIs, Responsive Web Design (RWD), Express.js, Software Engineering, Agile Software Development, Dashboards, REST API Architecture, Supabase, Booking Systems, OAuth
Senior Full-stack Engineer
2022 - 2023
Potion AI, Inc
- Developed new features for the AI platform using React, TypeScript, Node.js, NestJS, and GraphQL.
- Converted Figma designs into working responsive features.
- Fixed bugs on the back end using Node.js, NestJS, TypeScript, and GraphQL.
- Improved the search performance by 30% by refactoring queries.
Technologies: React, Node.js, Full-stack, JavaScript, SQL, Python, GraphQL, Slack, MacOS, Chakra UI, REST APIs, Storybook, Unit Testing, Software Engineering, HTML5, ECMAScript (ES6), User Interface (UI), UI Components, Front-end, RESTFul APIs, Responsive Web Design (RWD), Tailwind CSS, TypeScript, Agile Software Development, REST API Architecture, Supabase, OAuth
Senior Front-end Engineer
2022 - 2022
OzoneAI, Inc.
- Fixed bugs in the current platform using the Ruby on Rails framework.
- Helped the team fix and deploy a failing application in staging and production to AWS using AWS Elastic Beanstalk, Redis, Amazon RDS, Amazon CloudFront, and Amazon EC2.
- Added new features using React and JavaScript alongside Rails.
Technologies: JavaScript, TypeScript, React, Ruby on Rails 4, Amazon Web Services (AWS), PostgreSQL, AWS Elastic Beanstalk, Redis, Slack, MacOS, REST APIs, Storybook, Unit Testing, Software Engineering, HTML5, ECMAScript (ES6), User Interface (UI), Front-end, SQL, RESTFul APIs, Agile Software Development
Software Engineer
2021 - 2022
eBay
- Took part of the team of engineers that developed the certified refurbished admin tool as a front-end engineer, using Node.js, Express.js, React, Redux, TypeScript, JavaScript, and CSS.
- Implemented unit tests with Jest, Enzyme, and Cypress, code coverage with Jest, and used Prettier with ESLint for code linting.
- Maintained, added features, and fixed bugs on pages that have millions of daily views in collaboration with multiple teams.
- Created micro frontends POCs with Webpack Module Federation and Next.js to implement in future eBay projects.
- Implemented eBay's middleware packages for session handling and API calls in a Node.js server that runs concurrently with the front end.
- Worked with the Venus team in implementing new components to the listing page, which has millions of views daily.
- Collaborated with the MyEbay team in migrating legacy systems to a new architecture and redesigning my eBay pages using Marko.js, Node.js, and JavaScript.
Technologies: Node.js, JavaScript, React, Marko.js, Git, JSX, Jest, TypeScript, Express.js, ESLint, Webpack, CSS, HTML, Enzyme, Jira, Scrum, GitHub, Responsive Web Apps, Agile Software Development, SQL, Next.js, Front-end, Web Development, Slack, MacOS, NPM, Unit Testing, Software Engineering, HTML5, ECMAScript (ES6), User Interface (UI), RESTFul APIs, Responsive Web Design (RWD), Dashboards, REST API Architecture, OAuth
Software Engineer
2020 - 2021
Levvel
- Worked with a large team on the migration of a FoxPro system from a big company to a top-notch tech stack.
- Used React, TypeScript, Redux, Sagas, Redux Observables, Less, Webpack, and Material UI in the front end.
- Built REST APIs to handle the Node.js-based back end with NestJS, TypeScript, SQL Server, Redis, and TypeORM.
- Created scripts that generate schema views from SQL Server into TypeORM entities.
- Assigned as temporary tech lead for four months with an average of 92% sprint completion rate.
Technologies: Node.js, TypeScript, NestJS, React, Redux, Less, CSS, SQL Server 2015, Redis, Amazon RDS, Material UI, JSON Web Tokens (JWT), ESLint, Jest, Enzyme, Webpack, TypeORM, Bitbucket, PostgreSQL, Redux-Saga, HTML, Jira, Scrum, Git, Responsive Web Apps, Agile Software Development, SQL, Full-stack, jQuery, APIs, Front-end, Back-end, Web Development, Amazon Web Services (AWS), Slack, MacOS, Linux, Figma, Amazon S3 (AWS S3), REST APIs, Styled-components, Storybook, NPM, Unit Testing, Software Engineering, HTML5, ECMAScript (ES6), User Interface (UI), UI Components, RESTFul APIs, Responsive Web Design (RWD), Express.js, REST API Architecture, OAuth
Software Engineer
2015 - 2021
Instacarro
- Started as one of the first engineers in the company that evolved into one of the major startups in Brazil and Latin America with more than $55 million raised.
- Led the software development of numerous services and REST APIs for real-time geolocation, reporting, and mailing using Node.js, JavaScript, and TypeScript.
- Created serverless functions for event handling with the auction platform, mailing, and financial solutions, among others.
- Worked with notification systems using pusher, AWS Lambda, and Firebase.
- Implemented several AWS features to manage services in the cloud, such as RDS, EC2, ECS, S3, CodePipeline, Lambda, Cognito, SES, SNS, CloudFront, and others.
Technologies: HTML, CSS, Node.js, MongoDB, TypeScript, React, JavaScript, AWS Lambda, NestJS, Koa, Express.js, Twilio API, Google Calendar API, AWS Elastic Beanstalk, Amazon Simple Notification Service (SNS), Amazon CloudFront CDN, Amazon RDS, Git, Bitbucket, JSX, Firebase, Enzyme, JSON Web Tokens (JWT), Less, PostgreSQL, Redux, Redis, NoSQL, MySQL, Jira, Scrum, YouTube API, Responsive Web Apps, Agile Software Development, Bootstrap, SQL, Full-stack, APIs, Front-end, Back-end, Web Development, Amazon Web Services (AWS), Serverless, Twilio, Startups, Slack, Linux, Figma, AWS Step Functions, Amazon S3 (AWS S3), REST APIs, WebSockets, Material UI, Styled-components, NPM, Unit Testing, Software Engineering, HTML5, ECMAScript (ES6), User Interface (UI), UI Components, Responsive Web Design (RWD), Dashboards, REST API Architecture, Booking Systems, OAuth
Full-stack Developer
2018 - 2018
Kambda
- Worked with US clients using the Ruby on Rails framework.
- Developed new functionalities for fintech and healthcare portals.
- Fixed issues and migrated the legacy Rails app to newer versions.
Technologies: Ruby, Ruby on Rails 4, JavaScript, jQuery, HTML, CSS, Redis, PostgreSQL, RSpec, Ruby on Rails 5, Slack, Linux, Heroku, REST APIs, Unit Testing, Software Engineering, HTML5, ECMAScript (ES6), User Interface (UI), Front-end, SQL, RESTFul APIs, Express.js, Agile Software Development, REST API Architecture, OAuth
Experience
Reporting Tool for Delta Dental
Led the front-end development of interactive business analytics using React, TypeScript, and React Query. Brought Figma designs to life by creating UI components with Material UI, making sure they look great on all screen sizes and devices.
I implemented flexible integration, robust authentication, powerful reporting, data privacy, and custom branding. I integrated Bold BI reports to enhance IBA's reporting capabilities. The application was hosted securely on AWS for scalability.
Also, I documented the project and laid the groundwork for future enhancements.
I implemented flexible integration, robust authentication, powerful reporting, data privacy, and custom branding. I integrated Bold BI reports to enhance IBA's reporting capabilities. The application was hosted securely on AWS for scalability.
Also, I documented the project and laid the groundwork for future enhancements.
Calendar App for ITV
Added new features, fixed bugs, and maintained and refactored the Calendar App for a large TV-show company in the US using React, Node.js, JavaScript, Firebase, Jest, and CircleCI. This project included a undo and redo cache implemented with Redux and and HTML to PDF rendering tool.
Laser GG Sharing Service
Created a secure REST API to share 3D printing resources for a medium client in the US using Node.js, TypeScript, NestJS, GCP, and JWT. The service has been successfully used every day by thousands of users.
Education
2010 - 2015
Bachelor's Degree in Computer Systems Engineering
Pontifical Catholic University Mother and Teacher - Santiago, Dominican Republic
Certifications
MAY 2023 - PRESENT
Introduction to OpenAI API & ChatGPT API for Developers
Udemy
APRIL 2020 - PRESENT
NestJS Zero to Hero - Modern TypeScript Back-end Development
Udemy
Skills
Libraries/APIs
Node.js, React, REST APIs, React Redux, Twilio API, Redux-Saga, YouTube API, OpenAI API, Google Calendar API, Marko.js, jQuery, React Query, React Testing Library, Stripe, Stripe API, Vue, Linaria, Playwright, Zod
Tools
Slack, Git, GitHub, Bitbucket, Jira, Figma, AWS Step Functions, NPM, Amazon Simple Notification Service (SNS), Amazon CloudFront CDN, JSX, Webpack, CircleCI, RSpec, Tableau, Prisma, Amazon CloudFront, AWS CloudFormation, Terraform, AWS SDK, LaunchDarkly, TanStack Router
Languages
JavaScript, HTML, HTML5, ECMAScript (ES6), TypeScript, SQL, CSS, Less, Ruby, Python, GraphQL, CSS3
Frameworks
Express.js, NestJS, Redux, Bootstrap, Koa, JSON Web Tokens (JWT), Next.js, Tailwind CSS, Material UI, Jest, Ruby on Rails 4, Ruby on Rails 5, Angular, gRPC
Paradigms
Agile Software Development, Unit Testing, REST API Architecture, Scrum, Responsive Web Design (RWD), Design Patterns
Platforms
Vercel, MacOS, Linux, Google Cloud Platform (GCP), Firebase, Heroku, Amazon Web Services (AWS), Twilio, AWS Lambda, AWS Elastic Beanstalk, Azure, Docker, PDF.js
Storage
MongoDB, PostgreSQL, Redis, NoSQL, MySQL, Amazon S3 (AWS S3), SQLite, SQL Injection Protection, Amazon DynamoDB
Other
Software Engineering, Web Development, Full-stack, APIs, Front-end, Back-end, User Interface (UI), Material Design, RESTFul APIs, Supabase, Booking Systems, OAuth, TypeORM, Enzyme, Responsive Web Apps, Serverless, Startups, WebSockets, Styled-components, Storybook, UI Components, Dashboards, Amazon RDS, ESLint, Software Design, Computer Science, Algorithms, SQL Server 2015, Google Cloud Functions, Chakra UI, OpenAI GPT-3 API, OpenAI GPT-4 API, BI Reporting, OWASP, XSS Protection, Security, Full-stack Development, Single Sign-on (SSO), Tailwind UI, Minimum Viable Product (MVP), LangChain, Vite, Multitenancy, Chrome Extensions, DOM, RPC, Monaco, Webhooks, Row-level Security (RLS), Lovable, pdf-lib, Bun, Personally Identifiable Information (PII)
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