Principal Software Engineer (React + Node)

pubGENIUS

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Location: United States
Job Type: full-time
Work Format: 🌍 Remote Worldwide
Salary: Unknown
Posted: June 25, 2026

Job Description

pubGENIUS is a React.js and Next.js development agency and ad-tech startup. We build websites and apps for clients across the US and Europe, specializing in decentralized finance (DeFi, crypto, NFT, blockchain), fintech, and healthcare, with occasional work in e-commerce and other verticals.Beyond client work, we operate our own high-revenue web product with a website, mobile app, and machine learning systems powering our ad-tech optimization engine. Performance is not a preference here, it is a core requirement.

We are looking for a Principal Software Engineer, who will be the technical authority, responsible for all development, architecture decisions, and long-term technical strategy across a website, mobile app, and ML-powered ad-tech optimization systems.This is a full-time independent contractor engagement. You will work hands-on at a senior level where site speed and server performance are core success metrics. You will work directly with stakeholders to set technical direction, remove bottlenecks, and ship production-grade code.

Engagement Details:

Type: Full-time independent contractor
Hours: Full-time commitment expected
Location: Remote
Clients: US and Europe
Rate: Competitive, based on experience

What You'll Own

End-to-end technical ownership of a high-revenue web platform and mobile app
Architecture design and long-term technical strategy
Server-side rendering pipeline using Node.js, Fastify 5, and React 19
Data layer across MySQL and BigQuery
GCP infrastructure including Cloud Run, Cloud Build, and Global Load Balancer
Ad-tech integrations including Google Ad Manager, GTM, GTag, and GPT.js
Performance optimization at scale, where every millisecond counts
ML pipeline maintenance and optimization for ad-tech performance

Requirements

Must-Have Qualifications

These are non-negotiable. Please only apply if you have strong, production-proven experience in all of the following:

Node.js with TypeScript in production
React in a server-side rendering context
MySQL including database design, query optimization, and ORM usage
BigQuery for querying and managing large-scale datasets
GCP with hands-on experience in Cloud Run, Cloud Build, Cloud SQL, and Load Balancing. GCP certification is a significant bonus.

Nice-to-Have Experience

Ad-tech industry experience including ad serving, yield optimization, and programmatic advertising
Affiliate marketing experience, particularly with Anura and Everflow
Cloudflare including CDN configuration, caching strategies, and Workers
Fastify, especially Fastify 5 patterns
Flutter for mobile app contribution
Golang or Rust for high-performance service work
Machine learning applied to ad-tech optimization (not LLMs or agents)
Experience in DeFi, crypto, NFT, blockchain, fintech, or healthcare verticals

Benefits

Fully remote work
Flexible hours
Paid vacation and sick days

Application Process

We do not review applications via LinkedIn DMs or email. Please apply through the application link.
We do not work with staffing agencies or third-party recruiters. Direct applicants only.

pubGENIUS is an Equal Opportunity Employer; employment with pubGENIUS is governed on the basis of merit, competence, and qualifications and will not be influenced in any manner by race, age, colour, gender, religion, national origin/ethnicity, veteran status, sexual orientation, marital status, gender identity, mental or physical disability, or any other legally protected status.

🎯 Who is this job for?

This role is best suited for a Principal Software Engineer with 10+ years of experience leading architecture and building high-performance, production-grade web platforms at scale. The candidate should have expert-level skills in Node.js, TypeScript, React (SSR), MySQL, BigQuery, GCP, performance optimization, and scalable system design, with bonus experience in Fastify, Cloudflare, Flutter, Go/Rust, ad-tech, machine learning, or blockchain/fintech. They should be capable of owning technical strategy end-to-end, making architectural decisions, optimizing infrastructure and application performance, and collaborating directly with stakeholders in a fast-paced, remote environment.

💬 Potential Interview Questions

How would you architect a high-performance server-side rendered application using React, Node.js, and Fastify?
I would design a modular SSR pipeline, optimize server rendering and caching, minimize hydration costs, and ensure efficient request handling to achieve low latency and excellent Core Web Vitals.
How would you optimize MySQL and BigQuery for different workloads?
I would use MySQL for transactional workloads with proper indexing and query optimization, while leveraging BigQuery for analytical processing, large-scale reporting, and aggregation over massive datasets.
What are the key considerations when designing systems where every millisecond matters?
I focus on minimizing network latency, optimizing database queries, reducing server response times, implementing effective caching, profiling bottlenecks, and continuously measuring real-world performance.
How would you design a scalable architecture on Google Cloud Platform?
I would use Cloud Run for stateless services, Cloud SQL for transactional data, BigQuery for analytics, Cloud Build for CI/CD, and load balancing with autoscaling to ensure resilience and scalability.
How do you approach performance optimization in ad-tech platforms?
I optimize page load times, script execution, ad loading strategies, caching, asynchronous processing, and continuously analyze performance metrics to maximize both user experience and revenue.
How would you integrate machine learning into a production software platform?
I would treat ML models as production services with versioning, monitoring, feature pipelines, evaluation metrics, and fallback mechanisms to ensure reliability and measurable business value.
What architectural tradeoffs do you consider when choosing between Node.js, Go, and Rust?
Node.js excels at rapid development and I/O-bound workloads, Go offers excellent concurrency and operational simplicity, while Rust provides maximum performance and memory safety for performance-critical services.
How do you make long-term technical strategy decisions as a principal engineer?
I balance business objectives, scalability, maintainability, engineering productivity, and operational costs while establishing architectural principles that enable future growth.
How would you mentor senior engineers while remaining hands-on?
I lead through architecture, code reviews, technical discussions, and collaborative problem-solving while continuing to contribute directly to critical technical initiatives.
What distinguishes a Principal Software Engineer from a Staff or Senior Engineer?
A Principal Engineer owns technical direction across multiple systems, influences long-term architecture and engineering culture, aligns technology with business strategy, and creates organization-wide technical leverage beyond individual project delivery.

📋 Job Summary

pubGENIUS is hiring a Principal Software Engineer to lead the architecture and technical strategy behind a high-performance web platform, mobile app, and ML-powered ad-tech systems serving clients across the US and Europe. In this fully remote role, you’ll work hands-on with Node.js, TypeScript, React, MySQL, BigQuery, and Google Cloud Platform to build and optimize server-side rendering pipelines, scalable infrastructure, and performance-critical systems where every millisecond matters. You'll own technical direction end-to-end, driving architecture, infrastructure, and engineering standards while contributing directly to products spanning ad-tech, fintech, DeFi, blockchain, and healthcare. With flexible hours, paid time off, and the opportunity to shape both client projects and an established high-revenue product, this is an exceptional role for engineers who thrive on ownership, performance optimization, and large-scale technical leadership.