26 to 50 of 114 API Design Jobs in London

C# / .Net Software Engineer (Freelance / contractor)

Hiring Organisation
Qim info
Location
London Area, United Kingdom
collaborate with international clients and are looking for skilled contractors to support project-based engagements. 📄 Your responsibilities: The objective of this role is to design, build, and govern an API integration layer connecting multiple internal and external systems within a complex energy trading environment. 💼 Required technical skills: API … Integration Architecture: Strong expertise in API integration, REST API design and exposure, interface-driven architectures, integration-heavy environments, abstraction layers, system decoupling Backend Development: .NET Core, C#, API services, integration services Architeture & Platforms: Design of scalable and reusable integration layers, interoperability with multiple systems (internal ...

Principal Software Engineer (Payments)

Hiring Organisation
X4 Technology
Location
City of London, London, United Kingdom
their latest platform, provide technical expertise at both the architectural and hands-on development levels, and mentor junior team members. What You’ll Do: Design and build scalable payment applications and APIs Develop modern frontend interfaces and backend services Integrate with payment providers and financial systems Optimise database performance …/Angular), HTML5, CSS3 Backend: Python REST APIs Data: MySQL, PostgreSQL, Redis Cloud & DevOps: AWS, Docker, CI/CD, Kubernetes (nice to have) Architecture: API design, OAuth/JWT authentication, queues, webhooks, payment integrations Previous experience in Financial Services What We’re Looking For: Strong system design ...

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 ...

Solution Architect (Principal Consultant)

Hiring Organisation
Jobleads-UK
Location
Greater London, England, United Kingdom
transformation and ensuring data is protected and used ethically. Talan UK & Ireland provides a range of consultancy and outsourcing capabilities including programme management, market design and governance. We also have extensive and award-winning capabilities across cyber security, data privacy and digital transformation. We are IIP Gold accredited … recruiting an ambitious and technically accomplished Solutions Architect to join our Digital business unit as a Principal Consultant. You will lead the design and delivery of scalable, secure, and cloud-native platforms across Energy (including Low Carbon and UK regulatory systems), Financial Services, Public Sector, and Healthcare domains. This ...

Senior Developer

Hiring Organisation
Reed.co.uk
Location
London, South East, England, United Kingdom
Employment Type
Full-Time
Salary
£80,000 per annum
venture backed by the strength and stability of an established business. Key Responsibilities End-to-end development of high-quality, scalable SaaS platforms from design through deployment and maintenance. Architect and implement robust backend services primarily using Python and PostgreSQL. Develop and maintain responsive, performant front-end applications with … Provide technical mentorship and leadership to development teams, fostering best practices in coding, testing, and deployment. Participate in code reviews, architecture discussions, and system design decisions. Troubleshoot and resolve complex technical issues across the full stack. Ensure software security, scalability, and performance are maintained at all times. Keep abreast ...

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 ...

Technical Co-Founder / CTO

Hiring Organisation
BLACKLINE
Location
London, England, United Kingdom
required 3. Backend Intelligence Layer * User profiles + preference memory * Provider availability + scheduling logic * Workflow orchestration (requests → bookings → confirmations) * CRM integration ⸻ Core Responsibilities * Design and build the end-to-end AI concierge system * Select and integrate LLMs, voice models, and orchestration frameworks * Build WhatsApp automation (e.g. via Twilio … architecture that scales without degrading experience ⸻ Technical Requirements You should have strong hands-on experience in: AI/LLM Systems * Prompt engineering + agent design * Tool use/function calling * Memory systems (vector DBs, session memory) * Multi-step workflow orchestration Voice Systems * Real-time speech pipelines (STT/ ...

AWS Solution Architect - Senior Manager

Hiring Organisation
Anson Mccade
Location
Central London, London, United Kingdom
Employment Type
Permanent
high-performing cloud practice. This is an opportunity to work at the forefront of cloud transformation, partnering with tier-one clients across industries to design and deliver innovative, scalable, and secure AWS solutions. You'll play a pivotal role in shaping enterprise cloud strategies while leading complex transformation programmes. … strategy Certifications & Education AWS Certification (Associate or Professional - e.g. Solutions Architect, DevOps Engineer) Degree in Computer Science, Engineering, or related discipline Technical Expertise Architecture & Design Translating business needs into scalable cloud architectures Cost optimisation and cloud best practices Data & AI Experience with data platforms, analytics, and AI/ ...

Software Engineer - Data Platform for Trading

Hiring Organisation
Harrington Starr
Location
City of London, London, United Kingdom
large-scale financial data platform, modernising legacy enterprise systems while building scalable cloud-based services on AWS. Own SQL Server optimisation, backend service design, and API development in a high-impact platform modernisation initiative. What You'll Do Develop and optimise SQL Server queries, stored procedures, and data … processing logic Design and build backend services in Python or C# Modernise legacy platforms and improve system performance Build and maintain AWS-hosted services and APIs Collaborate with distributed engineering and product teams Top Skills Required Advanced SQL Server expertise (performance tuning, indexing, complex queries) – non-negotiable Backend development ...

Senior API / PHP Developer - Fully Remote (UK) - £80,000+

Hiring Organisation
Venchr
Location
Central London, UK
Senior API/PHP Developer – Fully Remote (UK) – £80,000+ Venchr is partnering with a fast-growing SaaS company that’s redefining financial management in the luxury and yachting sector. Their platform unites accounting, payments, FX, and project management into a single, powerful ecosystem — helping clients worldwide streamline complex … operations with ease. They’re now seeking a Lead PHP Developer with a strong focus on API architecture and backend systems to join their fully remote UK-based engineering team. In this role, you’ll take ownership of designing, developing, and optimizing APIs that power mission-critical services. ...

Solutions Architect

Hiring Organisation
Euro Car Parks
Location
Central London, London, United Kingdom
Employment Type
Permanent
Ireland providing specialist services to a wide range of blue-chip clients. The role We are seeking technical polyglots who enjoy both technical architectural design, hands-on coding and peer reviews, though also like the idea of the equally important social/client-facing aspect of the role. … development architecture as well as supporting business analysts and product owners in planning and story-mapping for new development. You will act as technical design authority (TDA) for delivery of technical stories and produce technical documentation artefacts to support the delivery process. Main Responsibilities Duties will include: The design ...

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 ...

AWS Solution Architect

Hiring Organisation
Anson Mccade
Location
London, United Kingdom
Employment Type
Permanent
Salary
£75,000
impact role delivering large-scale enterprise cloud transformation programmes using AWS. What the Role Involves: As an AWS Solution Architect (Integration Specialist) , you will: Design and deliver AWS cloud-native workloads using serverless, microservices, and containerised architectures Build scalable, resilient, and secure integration solutions across enterprise systems Develop … Salesforce, and Oracle What Youll Need: Hands-on experience as an AWS Solution Architect (Integration Specialist) with Lambda and Kubernetes (EKS) Strong knowledge of API design and security (API Gateway, OpenAPI, OAuth2, JWT) Experience with cloud-native frameworks such as Flask or FastAPI Solid understanding of Kubernetes ...

AWS Solution Architect - Associate Manager

Hiring Organisation
Anson Mccade
Location
Central London, London, United Kingdom
Employment Type
Permanent, Work From Home
impact role delivering large-scale enterprise cloud transformation programmes using AWS. What the Role Involves: As an AWS Solution Architect (Integration Specialist), you will: Design and deliver AWS cloud-native workloads using serverless, microservices, and containerised architectures Build scalable, resilient, and secure integration solutions across enterprise systems Develop … Oracle What You'll Need: Hands-on experience as an AWS Solution Architect (Integration Specialist) with Lambda and Kubernetes (EKS) Strong knowledge of API design and security (API Gateway, OpenAPI, OAuth2, JWT) Experience with cloud-native frameworks such as Flask or FastAPI Solid understanding of Kubernetes security ...

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 ...

Salesforce Solution Architect

Hiring Organisation
Response Informatics
Location
London, United Kingdom
Employment Type
Permanent
Description: We are seeking a hands-on Solution Architect 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 that requires working closely with multiple Client enterprise and domain architects, Salesforce … 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 the target-state architecture aligned to prioritized use cases Create architecture diagrams (logical, physical, integration flows) and document solution designs Design and govern ...

Front End React Developer

Hiring Organisation
Ascend Consulting
Location
North West London, London, England, United Kingdom
Employment Type
Full-Time
Salary
£40,000 - £80,000 per annum
will coordinate with the rest of the team working on different layers of the infrastructure. Therefore, a commitment to collaborative problem solving, sophisticated design, and quality product is important. Responsibilities Working in a team of Front-End engineers Writing clear & concise code Working closely with Back-End engineers Participate … architecture design code reviews API design with the Back-End engineers and other team members to establish more functional, cohesive code Create, maintain documentation while implementing the best coding practices standards Hands-on approach Participation in sprint rituals What you’ll need 6+ years experience developing large ...

Salesforce Solution Architect

Hiring Organisation
Response Informatics
Location
London, United Kingdom
Employment Type
Permanent
Define and own the end-to-end solution architecture across Salesforce, Data Cloud, and connected enterprise systems Analyze the existing BT 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 … standards Ensure scalability, performance, security, and maintainability of the solution Required Skills & Experience Core Experience 78 years of experience in solution architecture/system design roles Strong experience in enterprise system integration and API-led architecture Proven ability to work across complex, multi-team enterprise environments Experience aligning ...

Senior Java Application Engineer

Hiring Organisation
Experis
Location
Wembley, England, United Kingdom
from inception, including the implementation of health check endpoints, secure secrets management via Azure Key Vault, correct port configuration for container workloads, and stateless design principles compatible with Azure Container Apps (ACA). Technical Leadership & Mentorship Provide hands‐on technical mentorship to junior and mid‐level engineers by conducting … Collaborate closely with the Principal Architect to translate High‐Level Designs (HLDs) into clear, production‐ready implementation plans. Ensure the team understands architectural intent, design trade‐offs, and non‐functional constraints that must be adhered to. Quality Assurance & Testing Strategy Champion a comprehensive automated testing strategy, including unit, integration ...

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 ...

Modernisation Engineer ( Java Azure )

Hiring Organisation
Experis
Location
Wembley, England, United Kingdom
ability to read, review, and contribute to Dockerfiles and GitHub Actions workflows as a developer who understands the delivery pipeline their code passes through. API Mastery : Deep expertise in RESTful API design, OAuth2 authentication flows (including FusionAuth integration), and DMARC-compliant transactional email delivery using SendGrid. Testing ...

Senior C# Engineer - Agentic AI, AWS, .Net 9

Hiring Organisation
Smart Sourcer Limited
Location
City of London, London, United Kingdom
Employment Type
Contract
Contract Rate
From £800 to £900 per day
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 ...

Senior Software Engineer

Hiring Organisation
TRIA
Location
London Area, United Kingdom
code quality, and conduct structured code reviews across the delivery team. Work directly with the BA to translate business requirements into sound technical design and produce low-level design documentation. Make architecture decisions, present options clearly to non-technical stakeholders, and govern integration standards across the programme. Support … roles, with strong hands-on .NET/C# delivery. Demonstrable experience leading architecture decisions on production-grade systems, not just contributing to them. REST API design and integration experience at scale, including defining and governing integration standards. Microsoft SQL Server: schema design, query optimisation, and working knowledge ...

Lead .NET Engineer/Architect

Hiring Organisation
Tria Recruitment
Location
City of London, London, United Kingdom
Employment Type
Permanent, Work From Home
code quality, and conduct structured code reviews across the delivery team. Work directly with the BA to translate business requirements into sound technical design and produce low-level design documentation. Make architecture decisions, present options clearly to non-technical stakeholders, and govern integration standards across the programme. Support … roles, with strong hands-on .NET/C# delivery. Demonstrable experience leading architecture decisions on production-grade systems, not just contributing to them. REST API design and integration experience at scale, including defining and governing integration standards. Microsoft SQL Server: schema design, query optimisation, and working knowledge ...