Overview
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
* Architect and evolve scalable backend services in Python (FastAPI/Django/Flask).
* Design and operate RESTful APIs aligned with OpenAPI/Swagger.
* Implement authentication and authorization (OAuth2/OIDC, permissions, session management).
* Optimise relational database design and performance (PostgreSQL).
* Introduce caching, rate limiting, and queuing to meet performance goals.
* Integrate with AI pipelines and model-serving endpoints (async inference, streaming).
* Containerise services with Docker; maintain IaC with Terraform/CloudFormation.
* Operate services on AWS with CI/CD pipelines (GitHub Actions/Argo CD).
* Lead security hardening, monitoring, and compliance readiness.
* Own backup, disaster recovery, incident response, and runbook creation.
* Mentor engineers and communicate technical trade-offs to stakeholders.
Requirements
* 5+ years' backend development with Python (Django or Flask).
* Proven experience designing, scaling, and operating production REST APIs.
* Deep expertise in relational database design, performance tuning, and migrations (PostgreSQL).
* Strong knowledge of Docker, Git workflows, and AWS core services (EC2, VPC, IAM, S3, ALB/ELB, ECR/ECS).
* Familiarity with API versioning, testing strategies, and documentation best practices.
* Eligible for SC clearance (or ability to obtain; DV clearance required later).
* Excellent problem-solving, communication, and high ownership.
Desired Skills
* Experience with OpenSearch/ELK, Prometheus, or Grafana for logging/monitoring.
* Knowledge of compliance frameworks (ISO 27001, GDPR, NIST SSDF, OWASP ASVS/SAMM).
* Background in building and operating high-throughput, low-latency services.
* 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.
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