Lead Software Engineer

SR2 REC LTD; Greater London; Hybrid; GBP 84,000 - 99,000; Full time

Job summary

A fast-growing AI startup in London is seeking a Senior Software Engineer to take ownership of their backend platform. This hybrid role requires significant expertise in Python and service design, focusing on performance and reliability within a multi-tenant SaaS environment. The ideal candidate will have a strong sense of accountability and the ability to communicate effectively with both technical and non-technical stakeholders. Competitive salary range of £85k - £99k plus equity on offer.

Qualifications

• Strong experience in backend engineering and ownership mindset.
• Deep experience in service design using Python or another strong backend language.
• Solid knowledge of relational databases.

Responsibilities

• Own the backend architecture and ensure reliability across a multi-tenant SaaS platform.
• Design and evolve APIs, data models, and integrations.
• Make pragmatic trade-offs regarding scale, correctness, and maintainability.

Skills

Backend engineering

API design

Production systems

Python

Cloud platforms

Job description

Senior Software Engineer | London (hybrid) | £85k - £99k + Equity | Python | FastAPI | SaaS

Location: London (hybrid)

Salary: £84,000 to £99,000 plus equity

Tech Stack:

• Backend: Python (FastAPI), experience in any strongly typed language is required
• Frontend: TypeScript (Vue.js)
• Cloud Systems: experience across any GCP, Azure, AWS

Are you a Senior Backend Engineer who wants to own the backend properly, not babysit it?

We are working with a fast growing AI startup that is already live with enterprise customers, real revenue, and real technical complexity. The platform is multi-tenant, data heavy, and deeply tied to AI powered workflows.

You will take ownership of the backend platform and set the technical direction. This is a hands on senior role with genuine authority. You will write production code, make architectural decisions, and set the standard for quality across the team.

What you will be doing:

• Owning backend architecture, performance and reliability across a multi tenant SaaS platform
• Designing and evolving APIs, data models and integrations
• Making pragmatic trade offs around scale, correctness and maintainability
• Setting standards for backend quality, testing and observability
• Working closely with product and frontend engineers to ship end to end features
• Acting as the go to person for backend decisions

What they are looking for:

• A genuine senior backend engineer with ownership mindset
• Strong experience building and running production backend systems
• Deep API and service design experience in Python or another strong backend language
• Solid relational database experience
• Comfort making architectural decisions without over engineering

The ideal candidate is someone who takes ownership naturally and communicates with intent. They are comfortable being the point of accountability for backend decisions and can explain complex technical trade offs clearly to both technical and non technical stakeholders.

We are looking for someone who enjoys working collaboratively, challenges ideas constructively, and knows when to push back and when to align. They are calm under pressure, methodical when things break, and thoughtful about the impact their decisions have on users, teammates, and the wider system. They care about code quality, but they care more about building reliable software that works in the real world.

If you're interested, drop me an email at .

Senior Software Engineer | London (hybrid) | £85k - £99k + Equity | Python | FastAPI | SaaS