Senior Fullstack Software Engineer

Outsmart Insight Ltd; Greater London; Hybrid; GBP 70,000 - 100,000; Full time

Job summary

A growing engineering company in Greater London is seeking a Senior Fullstack Software Engineer responsible for designing, building, and maintaining critical production systems. The role emphasizes ownership, systems thinking, and high-quality engineering on mature platforms. The ideal candidate will have 8-15 years of experience, strong Python skills, and comfort navigating complex legacy code. This position offers an opportunity to make architectural decisions and contribute to the company's operational growth, while working alongside senior decision-makers.

Qualifications

• 8–15 years of experience in engineering roles.
• Experience in small teams without heavy processes.
• Strong operational maturity with production systems.

Responsibilities

• Designing and maintaining backend services using Python.
• Developing well-structured RESTful APIs.
• Improving data models across relational and NoSQL databases.
• Contributing to cloud-based infrastructure and DevOps practices.

Skills

Backend development

Python

Systems thinking

RESTful APIs

Cloud infrastructure

Tools

PostgreSQL

Google Cloud

Job description

The pitch. It’s a serious engineering role with a great team – and meaningful responsibility.

This is not a narrow “ticket-closing” developer job.

You won’t be handed tightly scoped Jira tasks inside a heavily layered team structure. You won’t be maintaining a disposable MVP. And you won’t be managing people.

Instead, you’ll be working on the core platform that underpins Outsmart’s crowdsourcing operations – a mature, revenue-generating system that has evolved over years and continues to scale.

If you enjoy owning real systems, thinking architecturally, improving legacy code thoughtfully rather than rewriting it, and being trusted to deliver without heavy supervision, this role will feel unusually well-matched.

The role

As Senior Fullstack Software Engineer, you will help design, build and maintain the production systems that power Outsmart’s platform.

You’ll work closely with our CTO, operating as a high‑agency individual contributor with genuine ownership across backend systems, infrastructure and platform evolution.

This is a role for someone who wants to:

• Work on real, live systems with meaningful operational responsibility
• Make architectural decisions, not just implement them
• Improve and extend an existing platform with care and judgement
• Help shape the engineering foundations for the next stage of company growth

You will be trusted to take product and operational requirements and translate them into robust, production‑ready solutions.

What you’ll be doing

• Designing and maintaining backend services primarily in Python
• Developing and evolving well‑structured RESTful APIs
• Designing and improving data models across relational (e.g. PostgreSQL) and NoSQL databases
• Contributing to cloud‑based infrastructure (e.g. Google Cloud), deployment pipelines and DevOps practices
• Debugging live production issues with a calm, root‑cause mindset
• Incrementally improving system architecture using sound design principles (including modular design, DDD‑style thinking, and pragmatic architectural patterns)
• Reviewing code, raising standards constructively, and contributing to a disciplined engineering culture
• Leveraging modern tooling (including AI‑assisted development) to improve quality and velocity

This is not greenfield experimentation. It is thoughtful, high‑quality engineering on systems that matter.

The environment

We are a small, intellectually serious company. That has advantages and responsibilities.

You will:

• Speak directly with senior decision‑makers when needed
• Operate without perfect documentation
• Balance speed with long‑term maintainability

This role suits someone comfortable with autonomy, accountability and cross‑functional collaboration.

Who this role is for

This role is designed for someone who is:

• 8–15 years into their engineering career
• Has worked in a small company (c. 5–30 people) or similarly lean environment without heavy process
• Experienced in inheriting and improving mature systems
• Comfortable reading and navigating complex legacy code
• Strong in systems thinking (trade‑offs, scalability, cost implications)
• Backend‑heavy, with strong Python expertise
• Operationally mature – you’ve supported production systems, not just built features

You are likely:

• Calm under pressure
• Direct but not ego‑driven
• Curious and thoughtful rather than dogmatic
• Comfortable challenging ideas constructively

If you primarily identify as a manager, a greenfield‑only builder, or someone who prefers heavy structure and layered sign‑off, this role is unlikely to be a good fit.