Senior Full Stack Engineer (BE focused)

About The OpportunityThis is an immediate hire. We are building something brand new — and this role is foundational to the quality, performance, and scalability of what we ship. We need someone who takes genuine pride in the craft of back-end engineering: an engineer who sees system architecture, data modeling, API design, and performance not as hidden infrastructure, but as the core engine of the product.This is a full-stack role with a back-end focus. While the primary ownership is the server-side architecture and data layer, this engineer is expected to contribute meaningfully across the stack — building UI components, understanding client-side state, and making informed architectural decisions end to end. This person will be one of the most senior engineers on the team, with real ownership over how our systems are built, scaled, and integrated across the platform.This role is on-site in Mountain View, CA. ResponsibilitiesSystem Architecture & API Development — Designing, building, and scaling robust, efficient back-end APIs that power our front-end, with a strong sense of what makes an API clean, secure, and performant.Data & Storage — Owning database schemas, querying patterns, and storage strategies; understanding how data architecture decisions directly affect the product experience and system scalability.Full-Stack Integration — Owning the full request lifecycle, from data persistence and messaging layers up to the API and UI interaction.Back-End Performance & Security — Implementing caching strategies, optimizing database queries, managing asynchronous events/messaging, and ensuring robust authentication/authorization.Front-End Contribution — Writing clean, maintainable code within our React/Next.js ecosystem to consume APIs and deliver cohesive user experiences.Test Coverage — Writing comprehensive unit, integration, and functional tests (focusing heavily on API and database reliability) that keep the codebase stable as it scales.Engineering Culture — Leading code reviews, mentoring junior and mid-level engineers, and helping define the engineering standards we hold ourselves to.This Engineer Will Work Closely WithFront-End Engineering Teams — Aligning early on API contracts, data hydration patterns, and service boundaries to ensure the client-side has the performant, logical endpoints it needs.Product & Design — Helping shape what’s technically feasible, flagging trade-offs and edge cases early, and translating product requirements into scalable system designs.Data/Infra Teams — Collaborating on shared back-end decisions, infrastructure deployment, and event-driven messaging architectures.Required QualificationsBack-End Framework & Messaging: NestJS on Node.js / Express, REST + OpenAPI/Swagger (Scalar), Kafka, Typescript.Data & Storage: MongoDB + Mongoose (migrations via ts-migrate-mongoose), AWS S3Auth & Integrations: NextAuth, JWT, Stripe, PersonaBuild / Infra / DevOps: Docker & docker-compose, GitHub Actions, AWSCore Front-End: React, Next.js (App Router), TypeScriptClient State & Data: TanStack React Query, Zustand, ImmerStyling: Tailwind CSS, Emotion, CSS Modules, PostCSSObservability: PostHog, Winstoni18n: next-intl, i18next / react-i18next, DittoTesting: API: Vitest, Supertest, mongodb-memory-serverWeb: Jest, React Testing Library, StorybookCode Quality: ESLint 9, Prettier, Husky, lint-staged, Knip, Code CoverageAvenue Code discloses salary range information based on our commitment to fairness and transparency. We consider a wide range of factors such as internal equity, geographic location, relevant education, qualifications, certifications, experience, skills, seniority, business or organizational needs, and others. At Avenue Code, it is not typical for an individual to be hired at or near the top of the range for their role, and compensation decisions are dependent on the facts and circumstances of each case. A reasonable estimate of the current range for a Full-Stack Engineer is from $155k to $157k yearly.Avenue Code reinforces its commitment to privacy and to all the principles guaranteed by the most accurate global data protection laws, such as GDPR, LGPD, CCPA and CPRA. The Candidate data shared with Avenue Code will be kept confidential and will not be transmitted to disinterested third parties, nor will it be used for purposes other than the application for open positions. As a Consultancy company, Avenue Code may share your information with its clients and other Companies from the CompassUol Group to which Avenue Code’s consultants are allocated to perform its services.