Senior Fullstack Software Engineer in London

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
• Working across the stack where needed, including JavaScript, modern HTML/CSS, and utility frameworks such as Tailwind
• 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.

Practicalities:

• Schedule: Monday to Friday
• Weekends: No
• Location: UK-based
• Working style: Hybrid (remote and London office)

Why Outsmart Insight? Outsmart Insight operates at the intersection of technology, intelligence and large-scale coordination. Our internal platform powers a global network and supports complex, high-trust client engagements. We are deliberately serious about quality, reliability and long-term thinking. As we grow, we are investing in strengthening our engineering foundations – building systems that are robust, scalable and thoughtfully designed. If you want to work somewhere where your engineering judgement genuinely matters, this is that opportunity.

Our values:

• Smart minds, working together
• Quality delivered every time
• Strong client relationships built on trust
• Hard work, rewarded
• A happy, healthy team

Apply: Send a short cover letter and a two-page CV to careers@outsmartinsight.com, outlining why this role, and this type of engineering work, appeals to you. Please note: only applications sent directly to this email address will be considered.