Senior II Engineer

Python is the dominant backend language.

Flask and FastAPI, with strong typing and Pydantic powering automated documentation and API definitions.

PostgreSQL at the heart of most services.

AWS for cloud hosted services, with heavy use of AWS Lambda serverless.

Docker on AWS ECS for uniform development and deployment.

Internal developer platform with a standardised paved road from code to production, plus managed preview environments and feature flags.

You will be a great fit if you have:

Several years operating as a senior backend engineer, with a clear track record of leading technical initiatives end to end across a product domain.

Experience contributing to the design of distributed systems in production , including the operational realities such as failure modes, observability, data consistency, and graceful degradation.

A track record of solving scaling problems , whether database scaling, throughput, latency, or cost. You can talk through a real example end to end: how you measured the problem, what you changed, and what the outcome was.

Experience designing and operating event driven architectures in production , including message queues or streaming systems, with a clear understanding of delivery guarantees, idempotency, and failure handling.

Strong design skills around APIs, service boundaries, and the flow of data from persistent storage through to clients.

Strong Python experience, including modern web frameworks (we use FastAPI with Pydantic and strong typing).

Deep working knowledge of SQL and relational data modelling.

Excellent collaboration and communication, including the ability to explain complex systems and tradeoffs to non technical stakeholders.

A strong product and customer mindset, with the judgement to balance shipping value against long term system health.

A high bar for code quality, testability, and operational maturity, and the habit of raising that bar through review and mentorship.

Experience working on complex permissioning or access control systems (multi tenant, role or attribute based, fine grained, audit driven, or similar).

Experience with end to end document management systems , especially solving problems of scale and applying strong security practices such as encryption, access control, data lineage, and retention.

Experience modernising legacy systems and migrating workloads with minimal downtime.

Experience with a data pipeline orchestrator.

Experience working at AI startups, including integrating with and building on top of AI and LLM based solutions.

Competitive Salary(our salary bands are benchmarked at the top end of the market)

Pension (your minimum contributions are 4% with 9fin matching up to 7%)

Private Medical Insurance

Paid sick leave with Income Protection for long periods of illness

Group Life Assurance

Season Ticket Loan&Cycle to Work schemes

25 holiday days per year

Local public holidays (with the ability to exchange them for alternative days)

Hybrid working model, to allow you the flexibility to decide how, where and when you do your best work

Work abroad for up to 3 months a year

1 month paid sabbatical after 5 years of service

Enhanced parental leave&flexible working arrangements available

Professional learning and development budget

Quarterly team socials

Summer and Winter company social events

At 9fin we are dedicated to building and promoting a fair and inclusive workplace where everyone can reach their full potential and truly belong. We recognize that building diverse teams enables a more creative and productive environment. If you’re excited about this role but your experience doesn’t perfectly align with the job description, we encourage you to apply anyway. You might just be who we’re looking for — either for this role, or perhaps another.