Full Stack Engineer

About the Role ClassWallet is modernizing a large, business-critical fintech platform. This role will help evolve our legacy Node.js/Express + MongoDB backend and multi-generation frontend toward a cohesive modern stack (NestJS, Next.js) while preserving stability. The engineer will shape scalable architecture, write tests, and leverage AI tooling as a force multiplier. What You'll Do

• Work across the full stack — data model, API contract, UI, and production behavior — contributing to domains as they move onto the modern stack.
• Recognize bad legacy patterns and don't repeat them — read the existing Express/MongoDB and Backbone/React layers, understand where they fell short, and apply better practices in new development rather than carrying old habits forward.
• Design for scale within real constraints — build solutions that scale even when they have to integrate with a rigid legacy system that can't be changed wholesale.
• Build on the modern stack — NestJS modules (DI, guards, interceptors) and Next.js apps (App Router, server components, typed clients).
• Understand the strangler-fig approach — how legacy and new run side by side, behind feature flags, with zero data loss and no downtime — and contribute to it without disrupting it.
• Model relational data carefully — help move money-bearing/transactional data from documents into a normalized SQL schema with real constraints and safe migrations.
• Write tests as a default — unit, integration, E2E.
• Spot and flag problems — the flaky test, the N+1, the missing index. Raise them clearly so they get prioritized, and pick them up when it makes sense.
• Use AI tooling efficiently while understanding and standing behind every line that lands. What We're Looking For
• 4+ years shipping production full-stack
• Strong TypeScript front and back
• NestJS (or deep Express/Fastify w/ DI grasp)
• Next.js/React (hooks, App Router, SSR/CSR)
• PostgreSQL or MySQL (schema, indexing, migrations)
• An eye for distinguishing good patterns from bad legacy ones
• Ability to design scalable solutions that fit within an existing, rigid system
• Testing discipline (Jest, Playwright/Cypress, Supertest)
• API design (REST, auth, backward-compatible evolution)
• Bonus: Experience migrating off a legacy codebase
• Fintech/payments/ledger
• Message queues (RabbitMQ/SQS/Kafka)
• MongoDB/Mongoose – Aggregation
• AWS/Docker/Kubernetes/CD
• Deliberate AI-agent use in production workflows
• Who you are: takes ownership and responsibility; eager to grow; judgment to spot bad legacy code and not repeat it; designs for scale inside rigid constraints; refactors and builds with better practices; communicates trade-offs clearly; raises issues and flags risks Compensation & Benefits
• ClassWallet is a positive, family-oriented team environment with encouragement, gratitude, and work-life balance.
• Salary and benefits commensurate with experience.
• ClassWallet.com is proud to be an Equal Opportunity Employer. Applicants are considered for all positions without regard to race, color, religion, sex, national origin, age, disability, sexual orientation, marital or veteran status.