Backend Engineer - Multi-Tenant APIs & AI (London)

Oscar Technology; City Of London; On-site; GBP 85,000 - 105,000; Full time

Job summary

Oscar Technology is seeking a Backend Engineer to design multi-tenant data and workflow services in Python and FastAPI, bridging a Java/Spring core with Python AI services. You’ll join a UK core team reporting to the Head of Engineering and collaborate with an India-based delivery organisation.

The role emphasizes production-quality delivery, security, auditing, and cost-aware architecture in a fast-paced enterprise environment.

Qualifications

• 5+ years in back-end engineering for production SaaS or platform systems.
• Real multi-tenant or enterprise-system experience covering isolation, permissions and auditability.
• Strong Python with FastAPI or comparable frameworks, solid SQL/PostgreSQL, and the ability to work at Java/Spring service boundaries.
• Production AWS experience, plus confidence with Git, CI/CD and Linux.
• Daily use of AI coding tools such as Cursor or Claude Code, and a considered view of where they help.
• A degree in engineering, computer science or a related field, or equivalent experience.

Responsibilities

• Design REST and asynchronous services in Python 3.11+ and FastAPI.
• Work at Java/Spring boundaries with PostgreSQL and async SQLAlchemy persistence.
• Implement tenant isolation, context, role-based access and configuration.
• Version and evolve contracts between core and AI services without breaking consumers.
• Report to the Head of Engineering as part of the UK core team.
• Ship through disciplined CI/CD alongside the India-based delivery organisation.
• Treat authentication, authorisation, secrets, input validation, OWASP awareness and audit trails as everyday engineering.

Skills

Python

FastAPI

PostgreSQL

AWS

CI/CD

Linux

Git

SQL

AI coding tools

Multi-tenant

Education

Engineering/CS degree or equivalent experience

Tools

OpenTelemetry

pytest

pytest-asyncio

Jenkins

SQLAlchemy

Job description

Oscar Technology is seeking a Backend Engineer to design multi-tenant data and workflow services in Python and FastAPI, bridging a Java/Spring core with Python AI services. You’ll join a UK core team reporting to the Head of Engineering and collaborate with an India-based delivery organisation.

The role emphasizes production-quality delivery, security, auditing, and cost-aware architecture in a fast-paced enterprise environment.