Senior Backend Engineer — Multi-Tenant SaaS (Python/FastAPI)

Maxwell Bond; City Of London; On-site; GBP 85,000 - 105,000; Full time

Job summary

Descrial in London is seeking a backend engineer to join the UK core team. You will design REST and asynchronous services in Python 3.11+ and FastAPI, work at Java/Spring boundaries with PostgreSQL and async SQLAlchemy persistence, and implement tenant isolation, RBAC and configuration.

You will deploy on AWS using EKS/ECS, RDS and S3, build tests with pytest, ensure observability with OpenTelemetry, and drive cost-aware, scalable solutions in a fast-moving, enterprise-grade SaaS environment.

Qualifications

• Real multi-tenant or enterprise-system experience with isolation, permissions and auditability.
• 5+ years in backend engineering for production SaaS or platform systems.
• Strong Python with FastAPI or comparable frameworks and solid SQL/PostgreSQL.
• Ability to work at Java/Spring service boundaries.
• Production AWS experience and comfort with Git, CI/CD and Linux.
• Daily use of AI coding tools and a considered view on 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, at Java/Spring boundaries with PostgreSQL.
• Implement tenant isolation, context, RBAC and configuration; evolve contracts without breaking consumers.
• Maintain unit and integration tests with pytest; ensure observability with traces, logs, metrics and alerts.
• Deploy and operate on AWS using EKS/ECS, RDS and S3; improve queries, caching, throughput and cost.
• Build queueing and orchestration for model-calling services with cost awareness.

Skills

Multi-tenant systems

Backend engineering

Python

FastAPI

PostgreSQL

Java/Spring

AWS

Git

CI/CD

Linux

AI coding tools

Engineering degree

Education

Engineering degree

Computer science degree

Tools

FastAPI

PostgreSQL

SQLAlchemy

AWS (EKS/ECS, RDS, S3)

CI/CD tools

Job description

Descrial in London is seeking a backend engineer to join the UK core team. You will design REST and asynchronous services in Python 3.11+ and FastAPI, work at Java/Spring boundaries with PostgreSQL and async SQLAlchemy persistence, and implement tenant isolation, RBAC and configuration.

You will deploy on AWS using EKS/ECS, RDS and S3, build tests with pytest, ensure observability with OpenTelemetry, and drive cost-aware, scalable solutions in a fast-moving, enterprise-grade SaaS environment.