Senior Full Stack JS Engineer

This role is suitable for a Senior Full Stack JavaScript Engineer with 5+ years of experience building scalable applications using React, Node.js, JavaScript, TypeScript, SQL, cloud platforms, microservices, REST APIs, OAuth, and SAML.

The candidate should be skilled in software architecture, design patterns, relational and NoSQL databases, code quality, analytical problem-solving, and translating complex business requirements into effective technical solutions.

They should be familiar with leading projects end to end, mentoring engineers, coordinating implementation and client discussions, explaining trade-offs and timelines, and communicating fluently in English while working with Eastern US time zones.

How would you design a scalable full-stack architecture for an AI-powered product using React, Node.js, TypeScript, and microservices?

I would separate the system into domain-focused services with well-defined REST or event-driven interfaces, keeping the frontend independent from backend implementation details. I would use TypeScript across services, centralized observability, containerized deployment, and cloud-managed infrastructure for scaling and reliability.

How do you structure a React application to remain maintainable as the product and team grow?

I organize the application by business features rather than technical file types, use reusable UI and domain components, and keep server state separate from local UI state. TypeScript, clear component contracts, automated tests, linting, and consistent code review standards help maintain quality.

What are the main considerations when designing RESTful APIs in Node.js?

I use resource-oriented URLs, appropriate HTTP methods and status codes, consistent error formats, validation, authentication, authorization, pagination, and versioning where needed. APIs should also be documented, observable, idempotent where appropriate, and protected against abuse.

How would you implement OAuth and SAML-based single sign-on in a web application?

OAuth or OpenID Connect is appropriate for delegated authentication with identity providers, while SAML is commonly used for enterprise SSO. I would validate issuer, audience, signatures, state, nonce, and token expiration, then map the external identity to internal users and roles securely.

How would you choose between PostgreSQL, MySQL, Redis, and a NoSQL database?

I would use PostgreSQL or MySQL when transactional integrity, relationships, and flexible querying are central. Redis is useful for caching, sessions, rate limiting, and short-lived data, while NoSQL is appropriate for high-volume, access-pattern-driven data that does not require complex relational queries.

How would you make a microservices-based system reliable and resilient?

I would define clear service ownership and contracts, use timeouts, retries with backoff, circuit breakers, idempotency, health checks, and centralized logging and tracing. I would also avoid unnecessary synchronous dependencies and use queues or events for workflows that can be processed asynchronously.

What AWS, Azure, or GCP services would you consider when deploying a production Node.js application?

I would typically use managed compute such as containers or serverless functions, a managed relational database, object storage, a cache, a queue, and centralized monitoring. The exact services depend on traffic, latency, compliance, deployment model, and the team’s operational capabilities.

How do you identify and improve performance issues in a React and Node.js application?

I start with measurements using browser profiling, application metrics, distributed tracing, and database query analysis rather than guessing. Common improvements include reducing unnecessary React renders, optimizing bundles and network requests, adding appropriate caching, and fixing inefficient queries or blocking backend operations.

How would you design an AI feature that calls an external model provider reliably?

I would isolate model access behind a backend service, validate inputs and outputs, enforce authorization and rate limits, and protect sensitive data. I would add timeouts, retries where safe, fallback behavior, prompt and model versioning, cost monitoring, and evaluation metrics for quality and latency.

How do you approach technical leadership when product requirements, timelines, and engineering quality conflict?

I clarify the business goal, present feasible options with explicit risks, costs, and timelines, and propose a staged solution when appropriate. I document decisions, break the work into measurable tasks, and protect critical quality requirements while making pragmatic trade-offs visible to stakeholders.

NineTwoThree AI Studio is a Boston-based, remote-first product design and engineering studio building AI-powered web and mobile products for global brands and startups.

As a Senior Full Stack JavaScript Engineer, you’ll lead projects end to end, shape technical strategy, mentor engineers, and deliver scalable solutions using React, Node.js, JavaScript, TypeScript, SQL, cloud platforms, microservices, REST APIs, OAuth, and SSO.

This is a 100% remote, full-time role open to candidates in Armenia, with flexibility for Eastern U.S. meetings; salary is not disclosed.

Apply for the opportunity to solve meaningful challenges with a high-caliber global team, work on cutting-edge AI products, enjoy strong benefits and professional growth, and help lead a rapidly growing company.