4 senior api developer jobs found in London

Senior .NET / Full Stack Developer – Hybrid – £600/day Outside IR35 | C# | Azure | Event-Driven Systems | Payments | API-Driven We have a unique opportunity for a Senior .NET / Full Stack Developer to join a payments company. As a Senior .NET / Full Stack Developer , you’ll play a key role in building and scaling a high-throughput payments platform as the business enters its next phase of growth. This includes launching new products, enabling new partner integrations, and expanding a platform that already powers multiple live financial services products used globally. You’ll be building on top of a modern, cloud-native platform built with .NET and Azure , designed around API-first architecture and event-driven microservices . The platform supports complex payment flows, partner integrations, and high-volume transaction processing. This is a hands-on senior engineering role where you’ll contribute to architectural discussions, drive engineering best...

Senior AI Engineer | £600/day Outside IR35 | 6-Month Contract Industry: Technology / Capital Markets Location: London - 3 days in office Job Type: Contract Our client, a forward-thinking technology organisation, is seeking a Senior AI Engineer to join a team building production-grade AI systems powered by large language models (LLMs). You will work closely with software engineers and product stakeholders to design, develop, and deploy scalable AI applications, focusing on multi-agent orchestration, intelligent tool integration, and reliable production workflows. Responsibilities Design and implement LLM-powered AI systems, including RAG pipelines, vector/knowledge databases, and agentic frameworks. Build and maintain production-grade AI applications with clean code, APIs, data pipelines, and robust error handling. Develop and maintain evaluation frameworks to measure and monitor system performance, accuracy, and reliability. Implement feedback loops...

Java Developer - SC Cleared Location: London (1–2 days onsite per month) Contract: Outside IR35 Rate: £600–£675 per day Duration: 12 Month Contract Start: Immediate / Short Notice Preferred Eligibility: Active SC Clearance required (DV clearance ideally) Overview An experienced Java Developer is required to build and maintain scalable, high-performance applications within a secure public sector environment. Requirements Strong experience with Java & Springboot Solid Java back-end development experience Experience working in public sector Strong understanding of API integration and system design Active SC Clearance required (DV clearance ideally)

Java Developer - SC Cleared Location: London (1-2 days onsite per month) Contract: Outside IR35 Rate: £600-£675 per day Duration: 12 Month Contract Start: Immediate/Short Notice Preferred Eligibility: Active SC Clearance required (DV clearance ideally) Overview An experienced Java Developer is required to build and maintain scalable, high-performance applications within a secure public sector environment. Requirements Strong experience with Java & Springboot Solid Java Back End development experience Experience working in public sector Strong understanding of API integration and system design Active SC Clearance required (DV clearance ideally)