Job SummarySenior Software Engineer – join Defaqto (part of Fintel) to design, build, and evolve our online systems and services while advancing AI‑assisted development across the entire software lifecycle.
Department:
Technology
Location:
London
What you’ll do
Design, build, and maintain highly scalable web services, APIs, and backend systems that handle real‑world production load with reliability and performance.
Champion and mature AI‑assisted development across the full SDLC — from specification and design through coding, testing, documentation and release — helping the team get more value from tools such as Cursor, Codex, Claude and Copilot.
Drive our adoption of spec‑driven development, turning product intent into clear, structured specifications that guide both people and AI tooling toward correct, high‑quality implementations.
Contribute to the AI‑powered features we build into our products for customers, ensuring they are robust, responsible and genuinely useful in a financial services context.
Collaborate directly with the product team to evaluate ideas and rapid prototypes, proposing clear technical plans that balance ambition with pragmatism.
Lead and drive the engineering team through delivery, from sprint planning and technical design through to deployment and post‑release iteration.
Architect and review solutions across the full stack, ensuring consistency in patterns, quality, and long‑term maintainability.
Define and uphold engineering standards including code review, testing strategy, CI/CD pipelines and observability practices – and evolve those standards for an AI‑augmented workflow.
Partner with product on rapid iteration cycles, keeping feedback loops short, reducing time‑to‑learn, and enabling the team to move with confidence.
Proactively identify and address technical debt, performance bottlenecks and reliability risks before they become problems.
Contribute to architectural decisions and be a meaningful voice in engineering‑wide discussions around direction, tooling and process.
Act as an escalation point for complex technical problems, providing clear thinking and solutions under pressure.
Champion a culture of psychological safety, continuous learning and high engineering craft within the team.
What you’ll need to succeedEssential requirements
Significant hands‑on experience building and operating highly scalable online systems and services in production environments, consistent with senior ownership and technical leadership.
Practical experience using AI‑assisted development tools (e.g., Cursor, Codex, Claude, Zed, Copilot or similar) as part of everyday workflow, with a clear view of where they add value and where human judgement remains essential.
Understanding of, or genuine enthusiasm for, applying AI across the whole SDLC — not just code generation, but specification, design, testing, documentation and delivery — and a desire to help others adopt these practices.
Strong proficiency in designing and building RESTful/gRPC APIs and microservices architectures, with a deep understanding of trade‑offs in distributed systems.
Solid experience with multiple data storage paradigms: relational databases (PostgreSQL, MySQL), NoSQL (MongoDB, DynamoDB, Redis) and the patterns that make each appropriate in context.
Proven ability to coach and mentor junior and mid‑level engineers through code reviews, pair programming, technical guidance and constructive feedback.
Experience translating ambiguous product ideas or early prototypes into structured technical proposals and delivery plans – spec‑driven thinking is a strong advantage.
Demonstrated ability to lead an engineering team through a full delivery cycle, from technical design to release, while maintaining momentum and quality.
Strong understanding of software engineering fundamentals: algorithms, data structures, system design, testing and operational concerns (monitoring, alerting, incident response).
Experience working in an agile, fast‑paced product environment with short iteration cycles and close collaboration between engineering and product teams.
Excellent communication skills – able to articulate complex technical concepts clearly to both technical and non‑technical stakeholders.
A track record of pragmatic, outcome‑focused decision‑making: balancing technical rigour with the need to ship and learn quickly.
Desirable requirements
Experience building AI‑powered product features (e.g., integrating LLMs, prompt engineering, retrieval‑augmented generation, or evaluating and monitoring AI outputs in production).
Experience defining team practices, guardrails or governance around responsible AI use in engineering.
Experience designing and consuming gRPC services, including protocol buffer schema design and inter‑service communication patterns.
Familiarity with event‑driven architectures and messaging systems (Kafka, RabbitMQ, SQS/SNS).
Experience with cloud‑native infrastructure and deployment patterns (AWS, GCP, Azure) including serverless, containerisation (Docker/Kubernetes) and infrastructure‑as‑code.
Exposure to stream processing or real‑time data pipelines at scale.
Experience with search technologies such as Elasticsearch or OpenSearch.
Prior experience in a tech lead or staff engineer capacity, with involvement in cross‑team technical decision making.
Contribution to open‑source projects, engineering blog posts or technical community involvement.
Familiarity with product analytics, feature flagging and experimentation frameworks to support rapid iteration.
Experience with security‑by‑design principles and implementing secure coding practices across distributed systems.
Your approach to work
Takes ownership without being territorial – shares knowledge freely, helps others grow, and cares about the success of the whole team, not just personal output.
Brings clarity to ambiguity – comfortable working from a rough idea or prototype and structuring thinking around it, increasingly capturing it as a clear specification.
Embraces new ways of working – excited by AI‑assisted and spec‑driven development and wants to help shape their adoption in a financial services engineering team.
Balances speed and quality deliberately – understands when to move fast and when to slow down, and can make that call with sound reasoning.
Communicates proactively – surfaces blockers early, shares progress openly, and keeps both engineering team and product stakeholders informed without being prompted.
Important to knowWe have offices in various UK locations and you will be expected to attend one of the offices at least 3 days per week:
Farringdon, London
Cwmbran, Wales
Haddenham
Right to WorkApplicants must already hold a legal right to work in the UK without time restrictions and without the need for future sponsorship. We are unable to provide Skilled Worker visa sponsorship.
Equality and DiversityFintel plc and all the businesses within it adopt a zero‑tolerance approach to discrimination on any of the protected grounds in the Equality Act 2010.
We are committed to providing equal opportunities to all current and prospective employees regardless of age, disability, sex, sexual orientation, pregnancy and maternity, race or ethnicity, religion or belief, gender identity or marriage and civil partnership.
We aspire to have a diverse workforce because, in our view, diversity enables better business outcomes. We also believe that a more inclusive workplace, where people of different backgrounds work together, ensures better outcomes for all staff. From application to interview, we place inclusion at the heart of all we do.
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