17 of 17 Contract API Design Jobs in London

Senior Web Application Developer ASP.NET MVC 5, C#, & React

Hiring Organisation
PCR Digital
Location
Hammersmith, London, United Kingdom
Employment Type
Contract
Contract Rate
£425 - £538/day Inside IR35 to Umbrella
years of Web application development experience consisting of strong C#, ASP.NET MVC 5, and React. Strong knowledge of Object-Oriented Programming, SOLID principles, common design patterns and RESTful API design and integration (experience with SOAP WebServices and XML/XPat) also required. We are looking … Server, Entity Framework, and React experience desirable to have HTML5, CSS3, JavaScript, jQuery. * Strong knowledge of Object-Oriented Programming, SOLID principles, and common design patterns. * Experienced in RESTful API design and integration; experience with SOAP WebServices and XML/XPath. * Skilled in using IoC containers (Autofac, Ninject ...

Senior Full Stack Developer (React & C#.NET)

Hiring Organisation
Adecco
Location
London, United Kingdom
Employment Type
Contract
Python (pyspark): Experience with data pipelines and analytics is a plus. Power BI: Familiarity with developing dashboards and data models. Architecture: Knowledge of microservices, API design, and event-driven architectures. DevOps/CI/CD: Experience with Azure DevOps, GitLab, GitHub Actions, or similar tools. Cloud Platforms: Proficient … Azure preferred). Databases: Strong skills in SQL Server, PostgreSQL, or other relational databases. containerisation: Experience with Docker and Kubernetes. Key Responsibilities Design & Develop: Create and maintain full stack applications using React JS and C#.NET Core. Build Services: Develop high-performance backend services and RESTful APIs with a focus ...

Senior Java Engineer (AWS, REST, SOAP) - Hybrid - Sussex

Hiring Organisation
Salt Search
Location
London, South East, England, United Kingdom
Employment Type
Contractor
Contract Rate
£500 - £700 per day
engineering discipline, independent problem-solving ability, and a commitment to building robust, scalable systems. You will work across modern cloud-native architectures, contribute to API and microservices development, and help drive best practices across the engineering organisation. Key Responsibilities Design, develop, and maintain high-quality Java applications using … Spring Boot. Build and optimise RESTful APIs and contribute to GraphQL service development. Develop cloud-native solutions using AWS services such as Lambda, API Gateway, DynamoDB, ECS, S3, and others. Contribute to microservices architecture, event-driven systems, and distributed design patterns. Implement CI/CD pipelines using tools ...

Full Stack Java Developer

Hiring Organisation
Brio Digital
Location
London, United Kingdom
Employment Type
Contract
Contract Rate
£500/hour
looking for an experienced Senior Java Developer to join a high-performing engineering team. You will take a lead role in the design and delivery of complex, enterprise-scale solutions, bringing strong Java, AWS, and API expertise to a programme that is making a real difference to patient … care across the country. KEY RESPONSIBILITIES Lead the design and development of robust, scalable Java-based applications across the programme Build and maintain cloud-native solutions on AWS, applying well-architected principles throughout Design, develop, and test REST APIs to a high standard, ensuring performance, reliability, and security ...

Senior FullStack Developer

Hiring Organisation
Adecco
Location
City of London, London, United Kingdom
Employment Type
Contract
Contract Rate
£600 - £650/day
with CI/CD , microservices , and event-driven architectures is essential, and knowledge of Python (pyspark) for data-driven workflows is advantageous Key Responsibilities Design, develop, and maintain full stack applications using React JS , C#.NET Core , and supporting technologies. Build high-performance backend services, RESTful APIs, and microservices with … calculations, and enterprise-grade BI solutions. Strong understanding of data modeling, performance tuning, and governance in Power BI. Architecture: Strong knowledge of microservices , API design , event-driven architectures , and distributed systems. DevOps/CI/CD: Experience with Azure DevOps, Gitlab, GitHub Actions, or similar. Strong understanding ...

Senior FullStack Developer

Hiring Organisation
Adecco
Location
London, South East, England, United Kingdom
Employment Type
Contractor
Contract Rate
£600 - £650 per day
with CI/CD , microservices , and event-driven architectures is essential, and knowledge of Python (pyspark) for data-driven workflows is advantageous Key Responsibilities Design, develop, and maintain full stack applications using React JS , C#.NET Core , and supporting technologies. Build high-performance backend services, RESTful APIs, and microservices with … calculations, and enterprise-grade BI solutions. Strong understanding of data modeling, performance tuning, and governance in Power BI. Architecture: Strong knowledge of microservices , API design , event-driven architectures , and distributed systems. DevOps/CI/CD: Experience with Azure DevOps, Gitlab, GitHub Actions, or similar. Strong understanding ...

Salesforce Solution Architect

Hiring Organisation
NEEV LIMITED
Location
London, United Kingdom
Employment Type
Contract
Term Contract (Initial 3 Months with possible extension) Role Summary We are seeking a hands-on Solution Architect (78 years experience) to lead solution design and architecture alignment for a multi-system Agentforce and Salesforce implementation within a large enterprise environment.. This is a highly collaborative, client-facing role … systems. Key Responsibilities Define and own end-to-end solution architecture across Salesforce, Data Cloud, and connected enterprise systems Analyze existing client architecture and design target-state architecture aligned to prioritized use cases Create architecture diagrams (logical, physical, integration flows) and document solution designs Design and govern API ...

Senior Web Application Developer (Full Stack)

Hiring Organisation
CPS Group (UK) Limited
Location
London, United Kingdom
Employment Type
Contract
Contract Rate
£450 - £525/day
Role: Senior Web Application Developer (Full-Stack) Specialism(s): eCommerce, ASP.NET MVC 5, C#, React, Migrations, Microsites, Cloud-Native, HTML5/CSS3/JavaScript, API, CI/CD, IoC Containers, Agile Type: Contract, Daily Rate Duration: 3+ Months Location: London Pay Rate: £450 - £525 per day (Inside IR35 … ready environment. Role Requirements * Develop and maintain complex web solutions using ASP.NET MVC 5, C#, and React * Support migration activities, ensuring clean architecture, scalable design, and efficient implementation * Produce secure, maintainable, scalable, and fault-tolerant code following SOLID principles and OO design patterns * Contribute to front-end development ...

Lead C# Engineer - Agentic Workflows & AI Engineering, AWS

Hiring Organisation
Smart Sourcer Limited
Location
City of London, London, United Kingdom
Employment Type
Contract
Contract Rate
From £800 to £900 per day OUTSIDE IR35
Looking For: SeniorStaff-level backend engineer with deep, current expertise in C# and .NET Core 8/9 , capable of architecting and leading the design of distributed REST API microservices at scale. Authority in AWS serverless architecture; Lambda-first, with strong working knowledge of API Gateway … agent orchestration, context management, custom commands/skills and scaling AI-assisted delivery across a team. Expertise across Aurora RDS MySQL and DynamoDB; schema design, access patterns, indexing, query tuning, single-table vs multi-table trade-offs, and pragmatic thinking around consistency, scaling and cost. Proven experience designing event ...

Full Stack Software Engineer

Hiring Organisation
Brio Digital
Location
London, United Kingdom
Employment Type
Contract
Contract Rate
GBP 450 Daily
looking for two experienced Senior Full Stack Software Engineers to join a high-performing engineering team. You will play a senior role in the design and delivery of modern, scalable web applications, bringing strong full stack expertise across Next.js, TypeScript, and AWS in a programme delivering meaningful impact across … services nationwide. KEY RESPONSIBILITIES Design and build high-quality, scalable full stack applications using Next.js and TypeScript Develop and maintain cloud-native solutions on AWS, following well-architected and security best practices Design, build, and consume RESTful APIs, ensuring performance, reliability, and security standards are met Write ...

Full Stack Software Engineer

Hiring Organisation
Brio Digital
Location
London, Baker Street, United Kingdom
Employment Type
Contract
Contract Rate
£450/day
looking for two experienced Senior Full Stack Software Engineers to join a high-performing engineering team. You will play a senior role in the design and delivery of modern, scalable web applications, bringing strong full stack expertise across Next.js, TypeScript, and AWS in a programme delivering meaningful impact across … services nationwide. KEY RESPONSIBILITIES Design and build high-quality, scalable full stack applications using Next.js and TypeScript Develop and maintain cloud-native solutions on AWS, following well-architected and security best practices Design, build, and consume RESTful APIs, ensuring performance, reliability, and security standards are met Write ...

Senior Full Stack Engineer

Hiring Organisation
Access Computer Consulting
Location
City of London, London, United Kingdom
Employment Type
Contract
Contract Rate
£400 - £440/day
This role is designed for engineers who have built and operated large-scale systems end-to-end, not those with superficial exposure or purely design-focused experience. Candidates must have strong experience of Java Full Stack, React, Kubernetes & Docker. Experience in building responsive, component based user interfaces using modern … front end frameworks. Hands on expertise in API design and development (REST/JSON), including versioning and backward compatibility. Experience with UI testing, component testing, and front end build tooling. Experience in CI/CD pipelines, GitOps workflows, A/B testing strategies and also automating the workflows ...

Contract Senior Software Engineer (Java or Python)

Hiring Organisation
SoCode Limited
Location
London, United Kingdom
Employment Type
Contract
Contract Rate
GBP 650 - 700 Daily
generated code for correctness, security, and financial accuracy Desirable, but no essential: Experience with Apache Airflow or similar workflow schedulers REST or GraphQL API design experience Knowledge of fixed income, FX, or derivatives products and associated P&L/risk methodologies ...

Contract Senior Software Engineer (Java or Python)

Hiring Organisation
SoCode Limited
Location
London, Baker Street, United Kingdom
Employment Type
Contract
Contract Rate
£650 - £700/day
generated code for correctness, security, and financial accuracy Desirable, but no essential: Experience with Apache Airflow or similar workflow schedulers REST or GraphQL API design experience Knowledge of fixed income, FX, or derivatives products and associated P&L/risk methodologies ...

Software Developer

Hiring Organisation
Randstad Technologies Recruitment
Location
London, United Kingdom
Employment Type
Contract
Contract Rate
£550 - £585/day
complex risk calculations and high-throughput financial data processing. This is an environment where your technical expertise in Object-Oriented Programming (OOP) and API design will directly impact global operations and regulatory compliance. Key Responsibilities Engineering: Build scalable, testable, and maintainable applications using .NET Core and RESTful APIs … systems. Collaboration: Work alongside Quants, Risk Managers, and Front Office teams to translate business needs into technical reality. Architecture: Participate in high-level technical design and architectural discussions to evolve the platform. Requirements Technical Core: Extensive experience in C#, .NET, SQL Server, and CI/CD pipelines. Domain Expertise ...

Backend Engineer

Hiring Organisation
Randstad Technologies Recruitment
Location
London, United Kingdom
Employment Type
Contract
Contract Rate
£500 - £522/day
Expert Developer: Java experience (Spring Boot, Bazel, Maven) with a focus on distributed services and Kubernetes (GKE). System Designer: Strong skills in API design (gRPC, GraphQL, REST) and relational databases like PostgreSQL. Cloud Proficient: Hands-on experience with GCP services, including BigQuery and Cloud SQL. Security Minded ...

Backend Engineer

Hiring Organisation
Robert Half
Location
London, South East, England, United Kingdom
Employment Type
Contractor
Contract Rate
Salary negotiable
Live platform Contributing to a shared transaction layer used across multiple products Collaborating with frontend and mobile engineers to deliver consistent experiences Key Responsibilities Design and build backend services end-to-end Contribute to platform and API design decisions Improve system performance and reliability Work within … evolving architecture with real production constraints Profile The Backend Engineer will have strong API and service development skills Experience working on transaction systems, payments, or eCommerce platforms is required Experience with GraphQL preferred Exposure to Elixir, Go, or similar backend technologies Ability to work effectively in ambiguous, fast-changing ...