Senior Full Stack Developer - C#/Azure/Kafka at Appvia, London, 6 Months, £600-£650 per day (Outside IR35)

Senior Full Stack Developer - C#/Azure/Kafka

Internal Title: Software Engineering Senior Consultant

Location: London, UK (Hybrid - typically 1-2 days per week in office/client site)

Contract: 6-month rolling contract

Rate: £600-650 per day, Outside IR35

Start: ASAP

About Appvia

Appvia is a specialist cloud, platform, and solutions engineering consultancy, helping organisations modernise software systems, improve developer productivity, and adopt cloud-native practices that enable long-term, sustainable delivery.

Our software engineering capability focuses on modern application development, cloud-native architecture, event-driven systems, and improving delivery outcomes through better engineering practices.

We work across complex, high-impact environments in both the public and private sector, delivering solutions where quality, scalability, reliability, and security are critical.

About the Role

We’re looking for a Senior Full Stack Developer to join Appvia on a new event-driven engineering engagement within a large-scale energy trading environment.

You’ll be part of a small engineering team building a new event-streaming capability alongside an established data platform organisation. The focus will be on designing and building event adapters and supporting services in C# on Azure, connecting source systems and trading data into a Kafka-based event streaming platform.

This is a hands-on role for an experienced engineer who can operate with a high degree of autonomy. You’ll be working across the service and integration layer, solving complex engineering problems where resilience, performance and low latency are particularly important.

You’ll have the opportunity to help establish a new capability from the ground up, while working within the engineering standards and practices of a much larger data platform.

The initial engagement is 6 months with a view to extend, and one of the positions is available for an immediate start.

Interview Process - 3 Stage

• Discovery conversation with Talent Acquisition
• Technical Interview with Engineering Team
• Final Interview with Leadership

Requirements

About You

You’re a strong commercial full-stack engineer who enjoys getting into the detail of how systems communicate, integrate and operate at scale.

You’ll bring:

• Strong commercial software engineering experience, with C# as your primary language
• Hands-on experience building services, integrations or adapters between systems
• Strong experience developing cloud-native applications on Microsoft Azure
• Experience with Apache Kafka or comparable event-driven / event-streaming technologies
• Good understanding of APIs, service integration and distributed systems
• Experience building resilient, reliable services for business-critical environments
• Ability to work autonomously and make sound engineering decisions with limited oversight
• Strong communication skills and the ability to collaborate effectively within a small engineering team
• A pragmatic approach to engineering, with a focus on delivering robust solutions rather than unnecessary complexity

Experience working within energy trading, financial services, trading platforms or other highly time-sensitive environments would be particularly valuable.

Responsibilities

• Design, build and maintain event adapters and supporting services connecting source systems to an event streaming platform
• Develop production-quality applications and services using C# and Azure
• Build integration logic across APIs, services, data sources and event streams
• Develop solutions that are resilient and performant for time-sensitive data
• Work with Kafka producers, consumers and event-driven architectures
• Collaborate closely with the wider data platform engineering organisation
• Help establish engineering patterns and practices for a new event-driven capability
• Troubleshoot and resolve complex technical issues across application and integration layers
• Make pragmatic architectural and engineering decisions within a fast-moving environment
• Contribute to a high-quality, collaborative engineering culture

Technical Skills

Core technologies:

• C#
• Microsoft Azure
• Apache Kafka / event streaming
• REST APIs and service integration
• Event-driven architecture
• Distributed systems
• Full-stack software development

Nice to have:

• Energy trading / financial services experience
• Trading platforms or market/exchange data
• Experience working with low-latency or time-sensitive data
• Azure data platform technologies
• Experience establishing new engineering capabilities or teams