Senior Backend Engineer - Python
Outside IR35
Hybrid - Oxford or London | Contract
Our client, a UK-based deep tech start-up, is seeking an experienced Senior Backend Engineer (Python & Django or Flask) to own and operate mission-critical backend services powering generative AI products. You'll architect, build, and run scalable APIs and data services end-to-end, collaborating closely with AI engineers to deliver new features from concept to production. This role offers the opportunity to shape the backend systems at the core of cutting-edge AI, with a strong focus on performance, reliability, and security.
Key Responsibilities
1. Architect and evolve scalable backend services in Python (FastAPI/Django/Flask).
2. Design and operate RESTful APIs aligned with OpenAPI/Swagger.
3. Implement authentication and authorization (OAuth2/OIDC, permissions, session management).
4. Optimise relational database design and performance (PostgreSQL).
5. Introduce caching, rate limiting, and queuing to meet performance goals.
6. Integrate with AI pipelines and model-serving endpoints (async inference, streaming).
7. Containerise services with Docker; maintain IaC with Terraform/CloudFormation.
8. Operate services on AWS with CI/CD pipelines (GitHub Actions/Argo CD).
9. Lead security hardening, monitoring, and compliance readiness.
10. Own backup, disaster recovery, incident response, and runbook creation.
11. Mentor engineers and communicate technical trade-offs to stakeholders.
Requirements
12. 5+ years' backend development with Python (Django or Flask).
13. Proven experience designing, scaling, and operating production REST APIs.
14. Deep expertise in relational database design, performance tuning, and migrations (PostgreSQL).
15. Strong knowledge of Docker, Git workflows, and AWS core services (EC2, VPC, IAM, S3, ALB/ELB, ECR/ECS).
16. Familiarity with API versioning, testing strategies, and documentation best practices.
17. Eligible for SC clearance (or ability to obtain; DV clearance required later).
18. Excellent problem-solving, communication, and high ownership.
Desired Skills
19. Experience with OpenSearch/ELK, Prometheus, or Grafana for logging/monitoring.
20. Knowledge of compliance frameworks (ISO 27001, GDPR, NIST SSDF, OWASP ASVS/SAMM).
21. Background in building and operating high-throughput, low-latency services.
22. Strong mentoring and technical leadership abilities.
This role is ideal for a high-agency engineer who thrives on building and operating scalable backend systems in production, with the autonomy to directly shape the core infrastructure of a fast-moving AI start-up.