Job Description

Senior Backend Engineer - Rust
Location: Remote (UK 3 hours)
Reports to: Engineering Manager
Salary: 70,000 - 100,000
Employment type: Full-time, permanent
Modern Milkman isn't just another delivery startup. We're a Certified B Corporation designing the milk round for the modern world; reconnecting households with local suppliers while cutting packaging waste and emissions from the supply chain.
Our technology platform is the engine behind that mission. Every Rust module, API, and database migration helps power a real-world system that delivers reusable packaging, reduces waste, and makes sustainable living effortless for over one hundred thousand of customers across the UK and US.
We move fast, build with intent, and balance environmental impact with engineering excellence. Joining the team means shaping software that has both purpose and technical depth.
Role Purpose
Modern Milkman is rebuilding the backbone of its technology platform. We're moving core business logic, order management, and operational workflows from a legacy C# microservices architecture into a new Rust-based modular monolith; faster, safer, and far more maintainable.
This role exists to both bridge and build. You'll own critical migrations from .NET into Rust while simultaneously developing new features and integrations that expand the capabilities of our next-generation system. Your work will directly shape how millions of deliveries, returns, and memberships run every week across the UK and US.
Team Structure
You'll report to one of Modern Milkman's Engineering Managers and collaborate closely with teams across the platform; starting with the Customer Team, where we build and evolve customer-facing systems.
We're a lean, fast-moving organisation, so roles aren't carved in stone. As priorities shift, you may embed with other teams driving operations, logistics, or membership systems. We value engineers who adapt quickly, take ownership beyond their immediate remit, and help keep the whole system moving forward.
Seniority & Scope
This is a Senior Software Engineer role. You'll be expected to make solid architectural decisions, explain them clearly to both engineers and non-technical stakeholders, and follow through with clean, working implementations.
You'll balance hands-on delivery with technical leadership, guiding peers through migrations, reviewing designs, and ensuring that new systems align with Modern Milkman's wider architectural direction. The right candidate combines curiosity with pragmatism: someone who values correctness and performance, but also understands deadlines and business trade-offs.
Work Location
We're open to fully remote candidates within compatible time zones (roughly UK 3 hours). The team is primarily UK-based and collaborates through Slack and Notion, so you'll need strong async communication skills and a self-driven approach.
We host mandatory company events a few times a year. They're for alignment, not bureaucracy; a chance to meet the humans behind the commits.
Technology Landscape
Our new platform is a fully modular Rust monolith, built with Actix-Web, leveraging Rust's performance and safety guarantees. We avoid heavy ORMs in favour of explicit SQL and type-safe data handling. Everything is thoroughly tested, built for resilience and correctness from the ground up.
The legacy world runs on C#/.NET, delivering value but increasingly out of alignment with our engineering standards. It remains critical to daily operations and will continue to coexist for some time, requiring thoughtful integration and migration.
We use PostgreSQL for new systems (with some remaining MS SQL Server workloads), Datadog for observability, and AWS as our primary cloud platform.
Performance Expectations
Success in this role will be measured by clear, operational outcomes rather than activity:

• Service quality: measurable improvements in availability, latency, and error rates across customer and operations journeys.
• Migration delivery: completion of defined C#-to-Rust migrations with no functional regression and clear performance gains.
• Engineering standards: creation and ongoing maintenance of clear, documented standards for Rust development, testing, and observability.
• Team discipline: fostering a culture of diligence, code quality, and operational accountability within the Customer Team and beyond.

You'll be expected to balance shipping features with raising the bar; ensuring every line of code contributes to stability, clarity, and long-term maintainability.
Key Responsibilities

• Design, build, and maintain performant Rust services within our modular monolith, using Actix-Web and explicit SQL.
• Migrate critical business logic from legacy C# systems into Rust, ensuring accuracy, performance, and observability.
• Identify, prioritise, and deliver improvements to reliability, latency, and error rates across customer and operations workflows.
• Maintain disciplined testing, code review, and documentation practices that set the standard for the wider team.
• Define and uphold engineering conventions; including module structure, observability, and deployment patterns, and ensure they are explained and adopted consistently.
• Collaborate with other teams (Product, Operations, Data) to translate domain problems into robust technical solutions.
• Support architecture and platform evolution, contributing to design discussions and long-term technical decisions.
• Participate in incident reviews and post-mortems, ensuring lessons are codified into future development.
• Offer technical guidance to peers when needed, by example rather than title.

What you'll bring

• You're a senior engineer who prefers clarity over ceremony. You care about correctness, reliability, and the integrity of the systems you build. You can explain technical reasoning clearly to both engineers and non-technical peers, and you don't lose patience when the details matter.
• You're deeply experienced in Rust, comfortable designing large, modular systems and reasoning about concurrency, performance, and correctness. You may not be a C# expert, but you're pragmatic enough to dive into it, extract what's valuable, and migrate it cleanly into Rust when needed.
• You balance speed with precision, document as you go, and leave systems cleaner than you found them. You're comfortable owning a problem end-to-end; from design and data model to deployment and monitoring. You like Rust because it enforces discipline, and you value that same discipline in your teams.
• If you see a broken abstraction, you fix it. If you see a messy process, you streamline it. You understand that the product and the system succeed together, not in isolation.

Benefits

• 25 days holiday, 8 bank holidays (5 flexible ones). Plus, your birthday off too!
• EMI Share Options
• Up to 6% matched company pension.
• Access to thanksBen, for a range of core & flexible benefits
• Employee discount off Modern Milkman products
• Enhanced parental leave & pay
• Life Insurance
• Cycle to work scheme & Octopus EV salary sacrifice
• In-person company events
• 300 working from home set up
• 300 L&D budget per annum
• 300 Health and Well Being budget
• Endless samples of our stock - Seriously, our category managers have us taste testing food and drinks all the time!
• Up to 4 weeks working abroad
• 2x volunteering days and team volunteering days
• Loads of company clubs to join, from book clubs (Page Churners), Running, cycling and swimming (Trotters and Plodders), 5 aside Football (Modern Milkman FC) and any other pun-related clubs you can think of.

Interview Process
This is typically what it looks like; Screening Call>Hiring manager call>Technical interview inc ways of working > Final Intro with Product Director/CTO
Candidate Experience ?? Due to the high volume of applications, it might take us a little longer to get back to you. Most feedback will be shared via email, and we make every effort to provide specific and constructive insights whenever possible
We strongly encourage candidates of all different backgrounds and identities to apply. We believe that our team is stronger with a variety of perspectives.

Skills Required