Principal .NET Developer

Principal .NET Developer

Contract Type:

Contract

Location:

Industry:

Contact Name:

Lili Arno

Contact Email:

lili@additionsolutions.co.uk

Posted:

10-Sep-2026

Job Description

Lead .NET Engineer

Contract | £450–£500 per Day | Outside IR35
Fully Remote | ASAP Start

We’re partnering with a digital IT consultancy to appoint an experienced Lead / Principal .NET Engineer to take technical ownership of a small, highly skilled engineering team supporting the reliability and performance of a high-volume messaging platform.

This is a senior, hands-on technical leadership role for someone who can set direction, make key architectural decisions, guide engineers and maintain high engineering standards while still staying close to the code.

The Opportunity

As Lead .NET Engineer, you’ll act as the team’s technical authority, taking ownership of technical delivery and helping shape the architecture, reliability and engineering quality of a complex messaging environment.

You’ll divide your time between architecture, design, code review and hands-on engineering, while also supporting the wider team through technical guidance, work allocation and problem-solving.

This is an excellent opportunity for an experienced .NET engineer who enjoys combining technical leadership with deep engineering involvement, rather than moving away from the code entirely.

Key Responsibilities

You’ll play a key role in leading technical delivery by:

  • Taking ownership of the technical direction of the team.
  • Making key architecture and design decisions across the platform.
  • Allocating work and helping engineers prioritise delivery effectively.
  • Guiding developers through complex technical challenges and removing blockers.
  • Spending approximately 50% of your time across architecture, design and code review while remaining hands-on where required.
  • Reviewing and challenging internal and third-party .NET code to maintain high engineering standards.
  • Improving automated testing, test strategy and end-to-end validation.
  • Developing robust test harnesses, mocks and stubs.
  • Strengthening monitoring, observability and reliability across a high-volume messaging pipeline.
  • Supporting the ongoing development of the team’s technical capability and engineering culture.
  • Using AI development tools appropriately, with clear judgement around where they add value.
  • Ensuring all committed code is fully understood, maintainable and technically defensible.
  • Promoting strong engineering practices across design, quality, reliability and delivery.

About You

You’ll be a highly experienced .NET engineer with a strong technical background and proven experience leading teams through complex engineering challenges.

You will also have:

  • Strong and current .NET engineering experience.
  • Proven experience operating as the technical authority within an engineering team.
  • Strong architecture and solution-design capability.
  • Excellent code-review skills with the confidence to challenge technical decisions where required.
  • Experience reviewing both internal and vendor-developed code.
  • Strong knowledge of automated testing and modern software-quality practices.
  • Experience with test harnesses, mocks, stubs and end-to-end validation.
  • The ability to diagnose and resolve complex technical issues.
  • Strong understanding of reliability, monitoring and platform performance.
  • A genuinely hands-on engineering approach with strong technical depth.
  • Experience mentoring and developing engineers.
  • The confidence to make, communicate and defend technical decisions.
  • The ability to raise engineering standards across a wider team.
  • Good judgement when using AI-assisted development tools within production engineering environments.

Why Apply?

This is a fantastic opportunity to take technical ownership of a highly skilled engineering team and play a significant role in shaping the reliability and quality of a complex, high-volume platform.

In return, you’ll benefit from:

  • £450–£500 per day
  • Outside IR35 engagement
  • Fully remote working
  • ASAP start
  • A senior technical leadership role with genuine ownership of architecture and engineering direction.
  • The opportunity to remain hands-on while influencing wider technical strategy.
  • Exposure to complex, high-volume and reliability-critical systems.
  • The opportunity to shape testing, monitoring and engineering best practice.
  • A role where strong technical judgement, leadership and engineering depth are genuinely valued.

We are an equal opportunity employer and value diversity at our company. We do not discriminate on the basis of race, religion, colour, national origin, gender, sexual orientation, age, marital status, veteran status, or disability status.

By applying you are confirming you are happy to be added to the Addition Solutions mailing list regarding future suitable positions. You can opt out of this at any time simply by contacting one of our consultants.

Apply Now

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