Back End Developer

Block MB; Greater London; On-site; GBP 90,000 - 120,000; Full time

Job summary

Block MB is seeking a Senior Backend Engineer to own Python-based backend systems, design scalable APIs, and work closely with data and frontend teams to deliver end-to-end features.

You will build and optimise APIs, handle large datasets, and contribute to AI-powered capabilities while evolving the platform architecture in a fast-moving product environment.

Qualifications

• Proven Python backend development experience.
• Experience building production APIs (FastAPI or equivalent).
• Strong SQL and relational database knowledge.
• Experience with large datasets and performance tuning.

Responsibilities

• Design and develop high-quality APIs and backend services.
• Work with large-scale datasets and optimise complex SQL queries.
• Build infrastructure to support new AI-powered functionality.
• Improve scalability, reliability and performance of the platform.
• Collaborate with data and frontend teams to deliver end-to-end features.
• Help shape technical decisions as the engineering team grows.

Skills

Python

APIs / REST

Async framework

SQL

Data-driven optimization

Tools

FastAPI

Job description

I've partnered with an established, highly profitable SaaS business that is going through an exciting period of growth. Their platform is used by leading financial and professional-services organisations to make better decisions from complex data.

They're looking for a Senior Backend Engineer to join their engineering team and play a key role in scaling their platform and developing a new generation of data and AI-powered capabilities.

The Role

You'll take ownership across the Python backend, working closely with product, data and frontend engineers to build reliable, scalable systems.

You'll be involved in:

• Designing and developing high-quality APIs and backend services
• Working with large-scale datasets and optimising complex SQL queries
• Building infrastructure to support new AI-powered functionality
• Improving the scalability, reliability and performance of the platform
• Working closely with data engineering and frontend teams to deliver end-to-end features
• Helping shape technical decisions as the engineering team continues to grow

Who You Are

• Strong commercial experience with Python
• Experience building production APIs using FastAPI or another modern async framework
• Strong SQL and relational database knowledge
• Comfortable working with large datasets and performance optimisation
• A track record of taking ownership of projects from idea through to production
• Someone who enjoys working autonomously and solving ambiguous problems
• Comfortable working in a fast-moving product environment

Nice to have: experience with analytical databases such as ClickHouse, Redshift or Snowflake, data-intensive products, TypeScript, cloud infrastructure or mentoring junior engineers.

The Environment

This is a high-autonomy engineering environment where you'll have genuine influence over how things are built.

They're looking for engineers who enjoy solving real problems pragmatically rather than over-engineering solutions. You'll have the opportunity to work across the stack, influence architecture and help shape the next stage of the company's technical growth.