13 of 13 Contract API Design Jobs in London

Boomi Architect

Hiring Organisation
Syntax Consultancy Ltd
Location
London, United Kingdom
Employment Type
Contract
Contract Rate
£500/day 500/day (Outside IR35)
. Start ASAP during Summer 2026. Key skills, experience + tasks will include: Boomi Solution Architect with a strong focus on Boomi/iPaaS, API Management, Event Streaming, integration architecture, governance + technical leadership. Integration Adoption & Project Onboarding - architecture engagement + onboarding of priority projects onto the strategic integration … platform (e.g. SDEC, S4H, DWIT). Production of project-specific integration designs aligned to approved iPaaS, API and Streaming patterns. Completion of architecture assurance reviews and design recommendations for onboarding projects. Support projects through technical discovery, design and implementation phases. Reusable Integration Asset Library: design ...

Integration Architect - Java, AWS, FS - OutsideIR35

Hiring Organisation
Sanderson Recruitment
Location
City of London, London, United Kingdom
Employment Type
Contract
Contract Rate
£550 - £600 per day + Outside IR35
connectivity across the clients core systems. Key Responsibilities: Own and evolve integration architecture aligned with enterprise standards Define and govern integration patterns across teams Design and deliver event-driven, API-first, and messaging solutions (NATS, REST) Lead end-to-end integration delivery, including hands-on development (Java/… Spring) Ensure scalable, cloud-native solutions on AWS Produce architecture artefacts (blueprints, contracts, ADRs) Guide teams on best practices, API governance, and event design Engage stakeholders and align cross-team integration efforts Primary Skills: Event-driven architecture and messaging systems (NATS, pub/sub, async patterns) API ...

Integration Architect - Java, AWS, FS - OutsideIR35

Hiring Organisation
Sanderson
Location
London, South East, England, United Kingdom
Employment Type
Contractor
Contract Rate
£550 - £600 per day
connectivity across the clients core systems. Key Responsibilities: Own and evolve integration architecture aligned with enterprise standards Define and govern integration patterns across teams Design and deliver event-driven, API-first, and messaging solutions (NATS, REST) Lead end-to-end integration delivery, including hands-on development (Java/… Spring) Ensure scalable, cloud-native solutions on AWS Produce architecture artefacts (blueprints, contracts, ADRs) Guide teams on best practices, API governance, and event design Engage stakeholders and align cross-team integration efforts Primary Skills: Event-driven architecture and messaging systems (NATS, pub/sub, async patterns) API ...

Backend Developer (Azure)

Hiring Organisation
Amtis Professional Ltd
Location
London, Euston, United Kingdom
Employment Type
Contract
Contract Rate
£425 - £475/day OUTSIDE IR35
outside IR35. This is a hands-on role working on a mature Azure-based backend platform, with responsibility across the full software lifecycle - from design and development through to testing, deployment and production support. You’ll be working with C#, .NET, Azure Functions, Azure SQL, Azure Service Bus, Azure … API Management and Azure DevOps, contributing to a platform that supports connected patient services. This role is particularly suited to a developer who can hit the ground running, work independently and own technical delivery end-to-end without requiring day-to-day technical supervision. What You’ll Be Doing ...

Senior Java Developer

Hiring Organisation
CODEVERSE LIMITED
Location
London, South East, England, United Kingdom
Employment Type
Contractor
Contract Rate
£300 - £400 per day
experienced Senior Java/Python Engineer to join a high-performing Agile engineering team delivering secure, highly available and scalable microservices and API platforms. You will be hands-on with modern engineering technologies, working across microservices, APIs, Kafka, cloud databases, containers and observability, while also providing technical leadership … mentoring junior engineers. Key Responsibilities Design and develop scalable Java/Python microservices and REST APIs. Build and operate event-driven solutions using Apache Kafka . Design and optimise AWS Aurora PostgreSQL databases and data platforms. Deploy and support applications using Docker and Kubernetes . Develop API ...

Fullstack Engineer (Backend)

Hiring Organisation
Randstad Technologies Recruitment
Location
London, United Kingdom
Employment Type
Contract
Contract Rate
£450 - £550/day
Opportunity You will join a high-impact development squad building commercial offerings on top of the thriving open-source Backstage framework. You will design and build backend systems, APIs, and developer portals that elevate the developer experience across external commercial clients and internal engineering teams alike. Your Impact Backend … API Systems: Design, build, and maintain scalable backend services and APIs primarily using TypeScript, Node.js, and modern web technologies. Developer Experience & Infrastructure: Build and operate infrastructure, developer toolsets, and CI/CD deployment pipelines to streamline engineering workflows. Engineering Excellence: Elevate code quality through technical RFCs, code reviews ...

Senior C# Engineer .NET 9/10, AWS Lambda, SQS, SNS Outside IR35

Hiring Organisation
Smart Sourcer Limited
Location
City of London, London, United Kingdom
Employment Type
Contract
Contract Rate
From £700 to £800 per day
Overview: Youll operate as the technical spearhead for a greenfield product build, reporting to the Director of Engineering. Expect deep backend engineering, distributed system design, and high-quality serverless delivery, plus the chance to adopt modern AI-assisted development practices as part of your workflow. What Youll Bring: Senior … ability to architect and lead distributed REST microservices at scale. Strong authority in AWS serverless engineering: Lambda-first mindset, hands-on experience with API Gateway, SQS, Step Functions, EventBridge and IAM. Deep data expertise across Aurora MySQL and DynamoDB: schema design, access patterns, indexing, query tuning, and pragmatic ...

Contract AI Software Engineer - DV Cleared

Hiring Organisation
NSD
Location
City of London, London, United Kingdom
Employment Type
Contract, Work From Home
Contract Rate
£450 - £650 per day
Experience with AWS or Azure Familiarity with Docker and Kubernetes Experience working in secure or highly regulated environments Strong understanding of software architecture and API design IT WOULD BE NICE FOR THE AI SOFTWARE ENGINEER TO HAVE. Experience with RAG pipelines and vector databases Knowledge of MLOps tooling ...

Net Developer

Hiring Organisation
Pontoon
Location
Bromley, London, United Kingdom
Employment Type
Contract
Contract Rate
£700 - £750/day
Develop and maintain high-quality software applications using .NET (4.5+/.NET Core) and Python. Collaborate with cross-functional teams to gather requirements and design effective solutions. Provide support to team members and stakeholders to ensure smooth project execution. Liaise with technical and business colleagues to understand functional requirements … deliver solutions that align with business objectives. Utilise your understanding of Web Services (REST, SOAP) to design and document APIs effectively. Work with MS SQL Server, including TSQL, SSIS, SSRS for database management and reporting. Utilise version control tools such as Git/Bitbucket and job scheduling tools like ...

S/4HANA - Coupa Integration Architect

Hiring Organisation
CBSbutler Holdings Limited
Location
London, United Kingdom
Employment Type
Contract
Contract Rate
Up to £558 per day + inside ir35
between Coupa and SAP S/4HANA. This is an opportunity to work on a high-profile global programme, owning integration architecture from initial design through to deployment, cutover and Hypercare. What you'll be doing: Designing and delivering Coupa SAP S/4HANA integrations across complex enterprise landscapes … Leading integration architecture, solution design and technical delivery Building and managing APIs including REST/JSON, OData, IDocs and BAPIs Supporting procurement process integrations covering: Supplier and Business Partner data Purchase Orders Goods Receipts Service Entry Sheets Invoices and payment status updates Master data synchronisation Working with integration platforms ...

Software Developer

Hiring Organisation
Randstad Technologies
Location
London, South East, England, United Kingdom
Employment Type
Contractor
Contract Rate
£559 - £600 per day
Basel III/IV, CCAR, counterparty limit monitoring, or live exposure calculations. Core Tech Stack: Expert-level C#/.NET (.NET Core), scalable API design, and solid OOP/architectural principles. Data & High Performance: Strong SQL skills, experience handling large data volumes, and working with event-driven/ ...

Software Developer (233204-1)

Hiring Organisation
Randstad Technologies
Location
London, South East, England, United Kingdom
Employment Type
Contractor
Contract Rate
£600 - £700 per day
Basel III/IV, CCAR, counterparty limit monitoring, or live exposure calculations. Core Tech Stack: Expert-level C#/.NET (.NET Core), scalable API design, and solid OOP/architectural principles. Data & High Performance: Strong SQL skills, experience handling large data volumes, and working with event-driven/ ...

Solution Architect - Integration - Salesforce

Hiring Organisation
SR2
Location
London, United Kingdom
Employment Type
Contract
Contract Rate
£650 - £750/day
drive architectural decisions will be essential. Responsibilities Define and maintain the end-to-end solution architecture across the rewards portal and wider Salesforce ecosystem. Design integration patterns across Salesforce, customer identity, APIs, mobile applications and enterprise platforms. Translate business and technical requirements into scalable, resilient and maintainable solution designs. … Define the architecture for SSO, customer identity integration and associated authentication journeys. Review and assure API designs, data flows, integration components and system dependencies. Support the design of mobile and in-app webview customer experiences. Produce architecture artefacts, solution options, design decisions and technical roadmaps. Coordinate suppliers ...