Principal Full Stack Engineer

About the Role:

As a Principal Full Stack Engineer, you will be one of Sleek’s most senior individual contributors, leading the architectural vision and end-to-end delivery of complex web applications and core platform services. You'll operate with a high degree of autonomy, solving ambiguous engineering problems while helping raise the technical standards of the wider engineering organisation.

In this role you will balance deep technical execution across the full stack—from intuitive user interfaces to scalable distributed backend systems—while championing developer productivity and embedding agentic AI workflows into our products.

Key Outcomes:
1. Full Stack Architecture & Product Delivery

Architect, build, and maintain production-grade SaaS applications across the entire stack using modern JavaScript/TypeScript, frontend frameworks (React/Vue), and backend environments (Node.js/NestJS).

Design resilient APIs, database schemas (Postgres, MongoDB), and cloud-native services capable of scaling with business growth.

Partner closely with Product, Design, and Engineering leaders to turn complex operational and financial challenges into simple, robust software solutions.

2. Agentic AI Integration

Architect and implement agentic AI capabilities and intelligent workflows into production applications (e.g., document processing, automated classification, and decision-support systems).

Establish reliability patterns for AI features, including guardrails, evaluation frameworks, fallback strategies, and observability for model behavior.

3. Harness Engineering & Engineering Productivity

Build and maintain engineering harnesses, automated workflows, and internal developer tooling that eliminate friction in the engineering lifecycle.

Introduce modern AI-assisted development tools (such as Cursor, automated test/documentation generators, and debugging aids) to significantly increase productivity across the entire engineering organization.

4. Platform Performance & Technical Leadership

Identify and eliminate performance bottlenecks in APIs, data pipelines, and backend microservices.

Mentor senior and mid-level engineers, lead technical architecture reviews, and raise the bar for code quality, testing, and system design across Sleek.

Requirements

Must-Have Requirements:

• Depth— 8+ years shipping and running production SaaS.
• Architecture— scalable distributed systems, APIs, and service boundaries you've had to live with.
• TypeScript / Node.js— years in this ecosystem, not a recent port from another language. Relational and document databases both.
• Full-stack ownership— you take a feature from schema to API to UI and out to production without handing off the parts you like least. You're strongest somewhere, but you're not helpless anywhere.
• Developer platform— you've built internal developer tooling, automation, and paved paths that other engineers depend on daily, and treated them as products with users rather than side projects.
• Cloud and operations— you deploy it, monitor it, respond to incidents, and continuously improve it in production. Observability and security are part of the job, not someone else's.
• Production AI — You've built and shipped AI-powered product capabilities (agents, intelligent automation, document processing, workflow orchestration, or similar) and understand how to evaluate, monitor, and improve them in production.
• Force multiplier— you've raised the people around you through mentoring and standards that outlast you.
• Autonomy — You thrive in ambiguous environments, proactively identify problems worth solving, and drive technical outcomes without relying on detailed task management.
  

What Success Looks Like

• You pick up ambiguous problems and come back with a direction to argue about, not just a list of questions.
• You use AI tooling aggressively on your own work, and you're honest about where it fails.
• You'd rather delete code than add it, and you can tell which is which.
• You say when something is a bad idea, including when it's ours.
• You leave the codebase and the people around you better than you found them.
• You treat production incidents as your problem regardless of who wrote the code.

Nice-to-Have Experience

• Our stack— NestJS, React or Vue, Postgres or MySQL, MongoDB, AWS, Kubernetes or Rancher.
• Tooling and observability— Cursor, Claude Code, or Copilot; Grafana, Prometheus, OpenTelemetry.
• Applied AI—agentic systems, multi-agent workflows, LLM observability, sandboxed agent execution, and AI data pipelines.
• Context— async work in globally distributed teams; FinTech, Accounting, Compliance, or RegTech.