Senior Backend Engineer

The Role

We're looking for a senior backend engineer to design, build, and own the API platform that powers our biometric identity and payments product. The platform handles real-time device communication, payment processing across multiple providers, KYC verification, and a permission system that spans organizations, roles, and devices.

This is a backend role focused on API design, service architecture, and data modeling. You'll make decisions that shape how the platform scales — choosing service boundaries, designing schemas that hold up under load, and integrating with third parties without coupling our codebase to their failure modes.

You'll also contribute to our Python SDKs and on-premise deployment story, but the core of the role is the API platform itself.

You'll join a small backend team where your decisions shape the architecture.

What You'll Work On

Core — API platform:

• Designing service architecture and database schemas for new domains
• Shipping API features end-to-end: models, endpoints, async workers, admin tooling
• Optimizing PostgreSQL queries and ensuring zero-downtime migrations on a production database
• Building reliable third-party integrations (payments, KYC, SMS) with retries, error handling, and observability
• Maintaining real-time communication via WebSockets between the platform and physical devices
• Code review, testing, and security as a core part of how you work
• Contributing to Python SDKs that external developers integrate against
• Supporting on-premise deployments — packaging, configuration, environment-specific behavior
• Writing technical documentation: API references, integration guides

Tech Stack

• Languages: Python (primary), Go (supporting services)
• Frameworks: Django (core), FastAPI, Flask
• Databases: PostgreSQL, MongoDB, Qdrant, Redis, TimescaleDB
• Auth: JWT, OAuth2
• Infrastructure: Docker, Kubernetes (Helm), GitLab CI/CD, AWS (S3, KMS), Sentry
• Testing: pytest, factory_boy — 75% coverage enforced in CI
• API Documentation: OpenAPI / Swagger

What We're Looking For

You design systems, not just code features. You can take a vague problem — "we need to support a new payment provider," "we need a new permission scope" — and translate it into service boundaries, data models, and integration contracts. You've done this before: schema design, choosing between sync and async paths, knowing when to introduce a queue vs a direct call, and when an integration deserves its own service.

You know PostgreSQL well. Not "I've used the Django ORM." You design indexes for the access patterns you actually have, write migrations that don't lock production tables, read query plans, and recognize an N+1 in review.

You think of the API as a contract. Versioning, error semantics, idempotency, pagination, backward compatibility. Your OpenAPI specs match reality. You design endpoints that are obvious to consume.

You take testing seriously. You write tests that catch real bugs — integration tests against a real database, not mocks that mirror your assumptions. You test permissions, edge cases, and error paths. Test code gets the same care as production code.

You've run background tasks in production. Retries, idempotency, at-least-once delivery, race conditions in distributed workers. Dramatiq or Celery — the concepts transfer.

Code review is engineering, not gatekeeping. You catch N+1s, IDOR vulnerabilities, missing error handling, broken backward compatibility. You give actionable feedback — and accept review on your own code without ego.

Requirements

Required

• 5+ years of professional Python backend development
• Production experience designing service architecture and database schemas for new domains, not just adding to existing ones
• 3+ years building APIs with Django / DRF
• Deep PostgreSQL: schema design, indexing, query optimization, zero-downtime migrations
• Production experience with async task processing (Dramatiq, Celery, or equivalent)
• Working knowledge of Redis (caching, locking, pub/sub)
• Solid testing practices: pytest, integration tests, test architecture for complex systems
• Experience with Docker and CI/CD pipelines

Strong Plus

• FastAPI or Flask in production
• Payment provider integrations
• KYC / identity verification systems (Veriff or similar)
• Multi-tenant SaaS architecture
• AWS (S3, KMS, encryption)
• Building and publishing SDKs or client libraries
• On-premise / self-hosted product deployments
• Kubernetes and Helm
• OpenAPI specification design

What We Offer

• Direct impact on a product used by real organizations handling sensitive biometric and payment data
• Engineering challenges that aren't toy problems — distributed systems, multi-provider integrations, real-time communication, on-premise deployments
• Architecture-level ownership on a small team
• Low bureaucracy, high ownership