Senior Software Engineer – AI Systems & Full-Stack Ownership

Portfolio Credit Control; City Of London; On-site; GBP 90,000 - 120,000; Full time

Job summary

Portfolio Credit Control is seeking a Senior Software Engineer to own the application and integration layer for a new generation of AI-powered products. The role spans backend, API design, MCP integration and frontend development with React and TypeScript.

You will design scalable REST/GraphQL APIs, implement agent-to-agent connectivity, and build production-grade frontend apps while collaborating with UX and product teams.

Qualifications

• Strong backend development experience in Python
• Production-grade frontend with React/TypeScript
• Experience designing REST and GraphQL APIs with authentication and versioning
• Hands-on MCP or comparable integration technologies
• Solid AWS expertise (Lambda, ECS, API Gateway, S3)
• Experience with distributed/event-driven architectures
• Good observability, testing and CI/CD practices
• Experience with data stores like MongoDB/OpenSearch/Databricks
• Secure and reliable integration of internal and third-party services
• Collaboration with designers to deliver accessible frontend applications
• Understanding of frontend performance and accessibility standards

Responsibilities

• Own the application and integration layer end-to-end, including APIs and frontend development
• Design, build and maintain MCP servers exposing systems, content and tooling to AI agents
• Develop agent-to-agent connectivity with message contracts, state management and retries
• Design scalable APIs using REST/GraphQL with auth, versioning and streaming (SSE/WebSockets)
• Build production frontends with React, TypeScript and JavaScript
• Collaborate with UX and product teams to deliver accessible, responsive interfaces
• Develop AI-specific UIs including streaming responses, citations and progress indicators
• Integrate with internal platforms and third-party services focusing on security and performance
• Establish automated testing (unit/contract/e2e) across backend/frontend
• Work with platform engineering on deployment, observability, logging and reliability
• Act as technical owner for app/integration layer and document architectural decisions
• Provide mentoring and code reviews to other engineers

Skills

Python

TypeScript/React

API design (REST/GraphQL)

MCP integration

AWS (Lambda/ECS/API Gateway)

Distributed systems

Observability & CI/CD

Datastores (MongoDB/OpenSearch/Databr)

Security & integration

Frontend collaboration

Accessibility

Tools

React tooling

Job description

Portfolio Credit Control is seeking a Senior Software Engineer to own the application and integration layer for a new generation of AI-powered products. The role spans backend, API design, MCP integration and frontend development with React and TypeScript.

You will design scalable REST/GraphQL APIs, implement agent-to-agent connectivity, and build production-grade frontend apps while collaborating with UX and product teams.