Python Backend Developer in London, United Kingdom

At Mustard Systems, we leverage statistical modeling to dive into sports events and help us make informed predictions about future outcomes. By utilising our unique datasets, advanced statistical models, and custom-built software, we strive to accurately forecast sports results.

We value quick delivery and real-world impact over perfect code. If you’re an engineer who thrives on solving problems quickly and enjoys a flexible, outcome-focused culture, you’ll fit right in.

What You’ll Work On:

The team is the layer that turns trading intent into action. The 5 person team builds the systems that combine live market state, model predictions and trader input, then route and place bets across real-world liquidity sources quickly, safely and reliably.

• You’ll work on event-driven trading systems written in Python and asyncio where latency, correctness and operational safety all matter. You’ll ingest high-volume market and trading messages from Kafka, react to fast-changing conditions, and help maximize execution quality, reliability and available capacity across multiple liquidity sources.
• You’ll build the operational tools traders rely on every day: high-density trading UIs that display hundreds of active selections, handle high-frequency websocket updates, and stay responsive under pressure.
• You’ll also improve observability (using OpenTelemetry) across critical trading paths, including latency metrics, structured logging, tracing, dashboards, heartbeats and alerting.
• This is engineering close to production impact, where timing, resilience and correctness directly shape outcomes.

We work with an agile approach, following a flexible plan that adapts to new information and opportunities as they arise. Developers are a core part of this process, taking full ownership of their software throughout its lifecycle—from design and development to testing, review, and production support.

Key Responsibilities

• Design and Build Impactful Features: Develop new features that align with and drive our business goals, delivering high-quality code that brings measurable value.
• Collaborate on Code Quality: Review and test code from teammates to ensure functionality, maintainability, performance, and quality standards.
• Support in Production: Take ownership of your team’s software in production, ensuring stability and quickly addressing any issues that arise.
• Cross-Team Collaboration: Work closely with other development teams on cross-functional projects, and partner with traders and quants to design and implement the best solutions to real business problems.
• Participate in Out of Hours Support for our Software Systems.

Core Tech Stack:

• Languages: Python (Python 3.10+, Asyncio), JavaScript/TypeScript for frontend work, and Go for select infrastructure
• Tools: RabbitMQ and Kafka for messaging, PostgreSQL and Redis for data storage
• Environment: Linux servers
• Observability: OpenTelemetry, Prometheus, Grafana and Zabbix
• AI tooling of your choice: Claude Code, Cursor, Codex, etc

Requirements

Must-Haves:

• Strong background in software development, with strong experience with Python.
• A degree in Computer Science or a numerical subject from a top university.
• Exceptional communication skills, enabling you to convey complex technical ideas clearly to both technical and non-technical audiences.
• Strong decision-making abilities, with a knack for making thoughtful trade-offs in both implementation and architectural choices, balancing innovation and practicality.
• Experience with web scraping and reverse engineering techniques, including working against bot protection tooling.
• At least 3 years experience in software development

Nice-to-Haves:

• Familiarity with building event-driven systems
• Comfort with Linux/Unix environments
• Track record of driving successful cloud migrations, ideally to AWS, including setting up secure, scalable account and access structures.

Benefits

Why join Mustard Systems?

• Hybrid working environment. We're in the office every Monday, Tuesday and Thursday, and work from home every Wednesday and Friday
• Work on cutting-edge systems in a competitive and innovative field.
• Collaborate with a smart, driven team, where your contributions directly impact business performance.
• Opportunity to drive the company’s technical direction and double its revenue in the next three years.

Comprehensive benefits, including:

• Competitive salary and significant bonus potential

• Enhanced pension match with salary sacrifice option.

• Health insurance and life assurance.

• Sabbatical leave after five years.

• 33 days of annual leave (including bank holidays).