A photo of Mario Campbell, looking at the right

I build products that scale — from architecture to launch.

Mario Campbell

Product-minded engineer with 10+ years shipping SaaS platforms, mobile apps, and backend systems across startups and scale-ups.

See my work Let's talk

Selected Work

Production systems across fintech, dev tools, healthcare, and social.

Featured Developer Tools / SaaS Founder, CTO & Lead Engineer

Flagify

Feature flag platform built from scratch. Go API with streaming SSE evaluation and targeting rules, four TypeScript SDKs (Node, React, NestJS, Astro) with typed codegen, a Go CLI shipped via Homebrew and npm, a VSCode extension that surfaces flag state inline, and a GitHub Action for deploy gating. Terraform-provisioned staging on AWS with real observability.

Result SDKs, CLI, VSCode ext, GitHub Action — all live
GoTypeScriptReactPostgreSQLTerraformAWSSSE
Social Platform / Mobile + API Founder, CTO & Lead Engineer

Vanguard

Social platform for martial arts academies and practitioners. Mobile-first with Expo and React Native, a NestJS API, geo-aware academy discovery via PostGIS, 3-tier JWT auth with Google OAuth and TOTP MFA, training feeds, and an AI assistant for personalized insights. Monorepo with mobile app, API, and marketing site.

Result Mobile in alpha, API production-ready, 28 data models across the stack
React NativeExpoNestJSPostgreSQLPostGISAWSOpenAI
Fintech / Wealth Management Architect & Lead Developer

Private Wealth Platform

Full-stack wealth management platform with client dashboard, admin console, and real-time portfolio tracking. WebAuthn passkey auth, multi-channel notifications (in-app, push, email), order and position management, KYC flow, and audit trails. Under NDA.

Result In production, serving active clients
TypeScriptNext.jsNestJSPostgreSQLWebSocketsAWS
Healthcare / Wellness Architect & Lead Developer

Centro de Rejuvenecimiento

Multi-platform healthcare platform for a rejuvenation clinic. NestJS API with a Socket.io real-time gateway, Next.js web and admin, React Native mobile on Expo, PostGIS for location-aware scheduling. Terraform-provisioned AWS infra with a signed-URL asset pipeline. Stateful AI assistant on LangGraph + OpenAI with Postgres checkpoints. Multi-auth: passkeys, TOTP, social login.

Result Production deploys across web and mobile, real-time chat and AI assistant live
NestJSNext.jsExpoPostgreSQLPostGISSocket.ioLangGraphTerraform

I don’t just write code — I ship products.

Over the past decade, I’ve built and led software across SaaS, fintech, crypto, and mobile — from early-stage MVPs to systems serving thousands of users in production.

I work across the full stack: React and Next.js on the frontend, Node.js and Golang on the backend, PostgreSQL and MongoDB for data, and AWS and Docker for infrastructure. I’ve led teams, defined architecture, and shipped products where the decisions actually mattered.

10+ Years building software
Full-Stack Web, mobile, backend, infra
Product-Led I think in outcomes, not tickets

Currently open to consulting, technical leadership, and high-impact collaborations.

Stack

Technologies I use to ship products end-to-end.

Frontend UI, mobile, and client architecture
ReactNext.jsReact NativeTypeScript
Backend APIs, services, and business logic
Node.jsGolangNestJSGraphQL
Data Storage, modeling, and streaming
PostgreSQLMongoDBPrismaKafka
Infra Cloud, containers, and observability
AWSDockerSentryWebSockets

I'm available for select projects, consulting, or leadership roles.

I'm open to collaborating on high-impact projects where I can bring strategy, execution, and code to the table. Let's chat and see how I can help.

Interested in working together? Email me or connect on LinkedIn