27 api developer jobs found in London

Mid-Level .NET / Full Stack Developer – Hybrid – £450/day Outside IR35 | C# | Azure | Event-Driven Systems | Payments | API-Driven We have a great opportunity for a Mid-Level .NET / Full Stack Developer to join a growing payments company. As a .NET Developer , you’ll be working as part of an experienced engineering team building and scaling a high-throughput payments platform. The business is entering its next phase of growth, launching new products, enabling new partner integrations, and expanding a platform that already powers multiple live financial services products used globally. You’ll be contributing to 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 development role where you’ll work closely with senior engineers to deliver reliable, scalable...

Lead .NET/Full Stack Developer - Hybrid - £700/day Outside IR35 | C# | Azure | Event Driven Systems | Payments | API Driven We have a unique opportunity for a Lead .NET/Full Stack Developer to join a payments company. As the Lead .NET/Full Stack Developer , you’ll play a key role in shaping 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 technical role where you’ll help drive engineering best practices, contribute to architectural decisions, and mentor...

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...

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)

Full Stack Developer (React / TypeScript / Java) Location: London (1–2 days onsite per month) Contract: Outside IR35 Rate: £650–£700 per day Duration: 12 Month Contract Start: Immediate / Short Notice Preferred Eligibility: Active SC Clearance required (DV clearance ideally) Overview An experienced Full Stack Developer is required to build and maintain scalable, high-performance applications within a secure public sector environment. The role requires a 50/50 split across front-end and back-end development . Requirements Strong experience with React and TypeScript Solid Java back-end development experience Experience working in a full stack capacity (approx. 50/50 front-end/back-end) Strong understanding of API integration and system design Active SC Clearance required (DV clearance ideally)

SharePoint/Microsoft 365 Application Developer £330-£350 per day | Outside IR35 | Fully Remote | 6-Month Rolling Contract | April Start We're looking for an experienced SharePoint/Microsoft 365 Developer to support digital transformation projects and deliver modern collaboration solutions across Microsoft 365. You'll design and build solutions across SharePoint Online, Power Platform, and wider Microsoft 365 services , helping organisations improve collaboration, automation, and productivity. What you'll be doing Build and maintain SharePoint Online sites, lists, libraries, and workflows Develop applications using Power Apps and Power Automate Create modern SharePoint components using SPFx Integrate Microsoft 365 services such as Teams, OneDrive, and Azure AD Support SharePoint migrations from Legacy environments Translate business requirements into scalable technical solutions Troubleshoot and improve SharePoint and Microsoft 365...

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)

Full Stack Developer (React/TypeScript/Java) Location: London (1-2 days onsite per month) Contract: Outside IR35 Rate: £650-£700 per day Duration: 12 Month Contract Start: Immediate/Short Notice Preferred Eligibility: Active SC Clearance required (DV clearance ideally) Overview An experienced Full Stack Developer is required to build and maintain scalable, high-performance applications within a secure public sector environment. The role requires a 50/50 split across Front End and Back End development . Requirements Strong experience with React and TypeScript Solid Java Back End development experience Experience working in a full stack capacity (approx. 50/50 Front End/Back End) Strong understanding of API integration and system design Active SC Clearance required (DV clearance ideally)

Fullstack Developer – Palantir Foundry job in London – £750 - £1000 a day – London – Outside IR35 Hexwired Recruitment is recruiting for an expanding Solutions provider, now seeking Data Engineers and Fullstack Developers with solid experience working on Palantir Foundry’s data analytics dashboard. You will be working on the full product lifecycle for a range of customers within Finance, energy and more. The successful candidate must have good experience on both the API development and backend data management side of Palantir’s products. Initial 3 months with very likely extension. Outside IR35 and will require at least 3 days onsite. Key Skills: Bachelors in CS, Maths, Physics or similar 3+ commercial Palantir Foundry dashboard experience Solid experience building applications using Palantir Foundry Excellent Data Engineering experience using Palantir Foundry Company is agnostic on programming languages, Python, Java, Typescript and/or React...

.Net 6, .Net 10, C#, ASP.NET, .NET Core, AWS, CDK, IaC, Cognito, S3, KMS, CI/CD, Docker, Containers, Entity, Firebase 3-month contract role. Outside IR35. £500 per day. Must be a UK based candidate. No visa sponsorship or visa transfer. Experience within Healthcare, Pharma or LifeSciences is a definite advantage. The role will involve the following: Migrate the platform to .NET 10 LTS Implement secrets management using AWS Secrets Manager Strengthen authentication and authorisation mechanisms Enhance audit trail and compliance features for healthcare regulations Improve API security, including rate limiting and CORS configuration Update Docker containers and CI/CD pipelines Establish and expand unit and integration test coverage Work with Clean Architecture patterns across the solution To start ASAP. Please email a CV to Roger at Jump IT in the first instance.

.Net 6, .Net 10, C#, ASP.NET, .NET Core, AWS, CDK, IaC, Cognito, S3, KMS, CI/CD, Docker, Containers, Entity, Firebase 3-month contract role. Outside IR35. £500 per day. Must be a UK-based candidate. No visa sponsorship or visa transfer. Experience within Healthcare, Pharma or Life Sciences is a definite advantage. The role will involve the following: Migrate the platform to .NET 10 LTS Implement secrets management using AWS Secrets Manager Strengthen authentication and authorisation mechanisms Enhance audit trail and compliance features for healthcare regulations Improve API security, including rate limiting and CORS configuration Update Docker containers and CI/CD pipelines Establish and expand unit and integration test coverage Work with Clean Architecture patterns across the solution To start ASAP. Please email a CV to Roger at Jump IT in the first instance.

Vue.Js, JavaScript, Vuetify, API, XSS, CSRF, Vite, Webpack, GitHub, AWS, Cognito, Firebase 3-month contract role. Outside IR35. £500 per day. Must be a UK based candidate. No visa sponsorship or visa transfer. Experience within Healthcare, Pharma or Life Sciences is a definite advantage. The role will involve the following: Lead the migration from Vue.js 2 to Vue.js 3 with Composition API Migrate Vuetify 2 components to Vuetify 3 Implement frontend security best practices (CSP headers, XSS prevention) Upgrade Node.js runtime Evaluate and implement Vite as the build tool Establish testing practices using Vitest and Vue Test Utils Optimise build performance with code splitting and lazy loading Work alongside a backend developer on API integration To start ASAP. Please email a CV to Roger at Jump IT in the first instance.

Boomi Integration Developer - Contract Overview We are looking for an experienced Boomi Integration Developer to support a series of integration projects. This is a 3‑month contract, fully remote, and operating outside IR35. Key Responsibilities * Design, develop, and maintain integrations using the Boomi platform * Work closely with internal teams to understand integration requirements * Troubleshoot and optimise existing Boomi processes * Support project delivery across multiple systems and data sources * Ensure best practice, documentation, and smooth handover at the end of the engagement Requirements * Proven experience as a Boomi Integration Developer * Strong understanding of integration patterns and API development * Ability to work independently and deliver in a fast‑paced environment * Excellent communication and problem‑solving skills * Boomi certifications beneficial but not essential Contract Details * Length: 3 months * Location: Remote * IR35 Status: Outside IR35...

Boomi Integration Developer - Contract Overview We are looking for an experienced Boomi Integration Developer to support a series of integration projects. This is a 3-month contract, fully remote, and operating outside IR35. Key Responsibilities * Design, develop, and maintain integrations using the Boomi platform * Work closely with internal teams to understand integration requirements * Troubleshoot and optimise existing Boomi processes * Support project delivery across multiple systems and data sources * Ensure best practice, documentation, and smooth handover at the end of the engagement Requirements * Proven experience as a Boomi Integration Developer * Strong understanding of integration patterns and API development * Ability to work independently and deliver in a fast-paced environment * Excellent communication and problem-solving skills * Boomi certifications beneficial but not essential Contract Details * Length: 3 months * Location: Remote * IR35 Status: Outside IR35...

Mulesoft Developer - Outside IR35 - 6 months We're looking for an experienced MuleSoft Developer to support an integration programme connecting enterprise systems including CRM and ERP platforms. You'll be responsible for designing and building integrations using the MuleSoft Anypoint Platform, working closely with internal teams to deliver API-led integrations and improve system interoperability. Key responsibilities Develop and maintain integrations using MuleSoft Build and document APIs using the Anypoint platform Support integration architecture and API specifications Debug, troubleshoot and resolve integration issues Write unit tests and maintain clean, well-structured code Support integration testing and deployment Experience required Strong hands-on experience with MuleSoft/Anypoint Platform Experience building API-led integrations Experience integrating CRM and ERP platforms Strong API, REST and...

Position: App Developer Location: Vauxhall/Stratford Day Rate: £600 p.d Outside IR35 Must hold active DV clearance A central government department is looking for an experienced App Developer to join a high-security programme. This role requires working on-site 5 days per week in Vauxhall, moving later to Stratford later on in the project. Due to the nature of the work, candidates hold UKSV DV clearance. Key Skills & Experience Strong expertise in Python, Docker, Kubernetes, and Data Governance Experience working in air-gapped environments, including managing dependencies and build pipelines without Internet access Proven background building APIs for data enrichment services Orchestration & data pipeline experience with Prefect or Airflow, and K8s or Swarm Configuration and automation of business workflow tooling (eg, Jira) Hands-on experience with a range of databases and storage technologies: Elastic, Mongo, Cassandra, Redis, S3 Desirable Skills...

Position: App Developer Location: Vauxhall/Stratford Day Rate: £600 p.d Outside IR35 Must hold active DV clearance A central government department is looking for an experienced App Developer to join a high-security programme. This role requires working on-site 5 days per week in Vauxhall, moving later to Stratford later on in the project click apply for full job details

Position: App Developer Location: Vauxhall/Stratford Day Rate: £600 p.d Outside IR35 Must hold active DV clearance A central government department is looking for an experienced App Developer to join a high-security programme. This role requires working on-site 5 days per week in Vauxhall, moving later to Stratford later on in the project click apply for full job details

Overview We are seeking a Senior Python Developer to support a large-scale digital transformation programme. The role focuses on building reliable Back End services, improving system performance, and contributing to a modern, scalable engineering environment. The client is open to strong EU-based talent. Role Detail: Contract Length: 3-6 months Rate: £250-400/day Outside IR35 (Depending on experience) Work Model: Fully Remote Key Skills and Experience Strong commercial experience with Python (Django) Solid understanding of REST APIs , microservices, and Back End architecture. Experience with cloud environments (AWS & Azure). Familiarity with CI/CD pipelines and modern DevOps practices. Strong understanding of relational and/or PostgreSQL. Ability to work in distributed teams and communicate clearly. Experience with Typescript and Svelte Good problem-solving skills and attention to detail. Nice to Have Experience with containerisation (Docker,...

The Value of Active Minds About Jupiter Jupiter is one of the UK 's leading investment management companies with just under 500 employees and £50.4 billion worth of assets under management (as at 30th September 2025). Jupiter provides investment services to individual and institutional investors through mutual funds (UK unit trusts, Luxembourg SICAVs and Dublin OEICs), separately managed accounts and sub-advised funds. Jupiter has experienced a period of international growth with offices open in EMEA and APAC. The majority of our employees are based in our London office located just minutes from Victoria station which provides stair-free access from both the Underground 's Victoria line and National Rail platforms, as well as limited road crossings to the Jupiter office. Our London office was designed to encourage employees to live active, healthy lives with floor-to-ceiling windows that allow for greater natural light and the benefit of a private balcony,...