Principal Software Engineer

Fintel

. Own Defaqto’s shift from AI-assisted coding to AI-led delivery .

Posted 9/19/2026full-timeLondon • United KingdomLeadWebsite

Core Competencies

Role fit

Core Competencies

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Demonstrates extensive experience in AI-assisted development, engineering standards, and practices across multiple teams, with a strong focus on API and integration engineering. Proven ability to lead cross-team architecture decisions and mentor senior engineers while connecting technical work to measurable business outcomes.

Highest-signal resume keywords

AI-Assisted DevelopmentAPI And Integration EngineeringData GovernanceCloud ArchitectureMentoring Senior Engineers

ATS Keywords

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Applicant Tracking System Keywords

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Hard Skills

.NET/C#TypeScriptPythonPHPSQLSpecification EngineeringTest-First ContractsCode ReviewDistributed SystemsCloud Architecture Judgement

Soft Skills

Influencing SkillsCommunication SkillsOwnershipAdaptabilityCoaching

Tools & Technologies

AzureMCP ServersCI/CDPolicy-As-CodeSelf-Service Tooling

Industry Keywords

Financial ServicesFintechRegulated DataFCAUK GDPR/ICO

Tech Stack

Tools & technologies

AzureCloudDistributed SystemsPHPPythonSQLTypeScript.NET

About the role

Key responsibilities & impact

Own Defaqto’s shift from AI-assisted coding to AI-led delivery
Define context and prompt engineering practices, agent-readable codebases and reproducible agent tooling
Raise standards for reviewing and hardening generated code using tests, static analysis and security scanning
Rebuild engineering practices around specification, acceptance criteria, architecture and verification
Run structured experiments with models, agents and workflows, measuring lead time, change failure rate, review burden and developer experience
Establish guardrails for secure, licence-aware and auditable AI-assisted development in a regulated business
Coach engineers through the shift toward engineering outcomes
Establish organisation-wide engineering discipline through templates, scaffolds, pipelines, linters, policy-as-code, automated checks and agent instructions
Define and evolve standards for code review, testing, branching, observability, security, documentation and definition of done
Own high-risk or high-upside initiatives end to end, including architecture, build, launch and operations
Design platforms and integration surfaces for developers and AI agents, including APIs, MCP servers, predictable errors, idempotency and rate limiting
Build data governance into technology through entitlements, licensing, lineage, provenance and auditability
Expose data quality and freshness signals through contracts and clear semantics
Improve consumption experiences through onboarding, keys, sandboxes, SDKs, documentation, analytics, versioning and deprecation
Partner with Product to validate feasibility, cost, risk and sequencing and identify technology-led opportunities
Guide multiple squads on technology choices and continuous improvement of the technology stack
Lead cross-team architecture decisions, document ADRs and maintain visibility of technical debt
Advise the Head of Engineering, CTO and leadership team on strategy and immediate technical trade-offs
Remain hands-on by building, reviewing and verifying critical work

Requirements

What you’ll need

Substantial commercial software engineering experience, including staff, principal or equivalent-level experience, with technical influence beyond your own team
Deep, current, hands-on engineering ability in a modern stack; core stack includes .NET/C#, TypeScript on Azure, Python, PHP, SQL and modern data tooling
Evidenced experience leading agentic and AI-assisted development in a production engineering organisation
Knowledge of specification and context engineering, test-first contracts, agent-readable codebases and rigorous code review
Ownership of engineering standards and practices across multiple teams, including embedding them in tooling and changing behaviour
Strong API and integration engineering, including designing, versioning, securing and operating interfaces
Experience engineering data governance through entitlements, licensing, lineage, provenance and auditability
Sound distributed systems and cloud architecture judgement covering resilience, observability, performance, cost and operability
Excellent influencing and communication skills across technical, product, commercial and executive audiences
Commercial instinct connecting technical work to measurable business outcomes
Mentoring track record that materially improves senior engineers
Comfort with a changing remit and owning the hardest current problem
Desirable: agent-facing integration surfaces such as MCP servers or tool-calling interfaces
Desirable: financial services, fintech or regulated data experience, including FCA and UK GDPR/ICO expectations
Desirable: data products, business intelligence or analytics platforms
Desirable: developer portals, API marketplaces or platform-as-a-product
Desirable: platform engineering, CI/CD, internal developer platforms, golden paths, policy-as-code and self-service tooling
Desirable: event-driven architecture and legacy modernisation or migration programmes
Applicants must already hold a legal right to work in the UK without time restrictions and without future sponsorship

Benefits

Comp & perks

Hybrid working arrangement with flexibility to work remotely for part of the week
Regular on-site collaboration with squads and product and leadership colleagues