Senior Full-Stack Engineer

• Own features end to end across the gateway middleware, backend API, and frontend - including schema design, API contracts, UI, tests, and rollout.
• Build and operate the subscription and usage-based billing system, including payment provider integration, webhook reliability, usage-to-invoice mapping, and entitlement enforcement.
• Design and implement guardrails that inspect and enforce policy on LLM prompts and completions, with per-tenant configuration and full auditability.
• Extend the telemetry pipeline and analytics aggregations that power customer-facing cost and usage reporting, and add tracing, metrics, and alerting across services.
• Write middleware that runs in the live request path, treating latency, failure modes, and graceful degradation as first-class design concerns.
• Design multi-tenant data models with correct isolation between organizations, workspaces, and keys.
• Write meaningful automated tests for the code you ship.
• Participate in architecture decisions, code reviews, and planning; document decisions for a distributed team.
• Handle sensitive data responsibly - secret encryption at rest, least-privilege access, and audit logging.

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• 5+ years of professional full-stack experience. You have built and shipped production SaaS features across the backend and frontend.
• Strong Python skills and experience building production APIs with FastAPI (or Django REST / Flask, with a willingness to work in FastAPI), including async programming
• Strong React and TypeScript skills - comfortable with component-driven UI, SPA state management, routing, and integrating REST APIs including streamed responses
• Practical familiarity with LLM integrations, retrieval-augmented generation (RAG), AI agents, or AI tools such as Cursor, Claude Code, or Copilot. You do not need an AI research or specialist agent infrastructure background.
• Experience with Stripe or a similar payment provider. Relevant work includes subscriptions, webhooks, idempotency, proration, refunds, and usage-based billing in production.
• Solid PostgreSQL skills: schema design, migrations, indexing, and query optimization - including aggregations over large event/log tables
• Experience with multi-tenant architectures, authentication and authorization, and tenant data isolation
• You can use Docker and run services in Kubernetes. You can read a Helm chart and debug a failing pod.
• Experience with Redis or a comparable cache, and with designing for cache correctness and invalidation
• You work well in a startup with limited structure. You clarify unclear problems, choose practical solutions, and deliver them with little oversight.
• Clear written and spoken English for collaboration and documentation

Nice to Have:

• Experience working directly with customers to define, build, and improve solutions.
• Experience with LLM API streaming, token accounting, rate limits, retries, and cost tracking.
• Experience building guardrails, content moderation systems - or working on trust & safety, compliance, or security tooling
• Familiarity with LLM gateways or proxies or with building an internal LLM platform
• Experience with LLM observability and evaluation tooling and with building evaluation harnesses
• Experience with usage metering and rating systems - turning high-volume event streams into accurate, auditable billable quantities
• FinOps or cloud-cost-optimization background; experience showing customers where their money goes
• Terraform and infrastructure-as-code experience on GCP (GKE, Cloud SQL, Secret Manager) or an equivalent cloud

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