Senior Net Developer Jobs in Plainfield, IL (NOW HIRING)

Who We Are

McMasterCarr is a leading ecommerce company that industrial customers have trusted for more than 120 years. Our products help customers restore manufacturing lines quickly, keep operations running smoothly, and prototype the next generation of innovative products.

We earn that trust by offering the right products, making them easy to find, and delivering them fast--so customers can solve problems with speed, precision, and confidence. This role is a pathway to senior engineering management and technical leadership-your growth is determined by your impact, not by tenure.

Our Culture

We intentionally cultivate a culture focused on clear execution and longterm growth. We are responsible for building systems that endure for decades and support the company's long-term growth. That responsibility means engineering work starts with a deep understanding of the problem and its impact, grounded in clear ownership, open communication, and direct feedback. Our teams are trusted to make thoughtful decisions about how work gets done, balancing a high bar for quality with practical execution. As an engineering leader here, you'll have significant autonomy with end-to-end ownership where you make product decisions while building things real people interact with directly.

How You'll Make An Impact

Our engineering teams operate within domains: distinct, highimpact areas of our platform that let engineers dive deep, build expertise, and release work that matters. Right now, we're actively growing in the following areas:

• McMaster.ai: Build and scale our domain-expert AI assistant that turns McMaster's product data and customer history into a continuously learning assistant-interpreting intent, narrowing options, explaining tradeoffs, and carrying context across sessions to make complex industrial work feel effortless.
• Customer Navigation: build and evolve the systems that help our customers find, evaluate, and understand millions of industrial products across our digital publications, including improving search relevance with LLMs and simplifying navigation across our product offering.
• Order-to-Payment Flow: design and evolve endtoend ordering experiences that reduce friction from checkout to mobile ordering.
• Product Merchandising: strengthen the internal platforms that power sourcing, inventory planning, receiving, and supplier relationships, helping the company make disciplined investments and scale responsibly.
• Fulfillment & Automation: lead development of software that integrates with warehouse operations, fulfillment, delivery, and customer service to reduce manual work and get orders to customers faster.

What You'll Do

• The first 30 days are about learning with purpose: understanding our goals, getting a clear picture of the customer journey, and building fluency in the codebase. As you onboard, you'll design and implement features that are small enough to help you ramp quickly, but substantial enough to matter.
• After you've delivered your first features, you'll start taking on lessdefined challenges where you'll sharpen requirements and produce thoughtful, durable solutions that meaningfully improve the customers experience. In doing so, you'll create clarity and momentum that enables you and your teammates to deliver exceptional experiences.

What You Bring

• 4+ years of professional fullstack or backend software engineering experience (see our Software Engineer II role for earlier career experience)
• Experience in delivering proofofconcepts and resilient production systems, contributing from early research and architectural design to development, launch, and iterative refinement.
• Ability to write high-quality, maintainable, and scalable code with Systems Design and SOLID principles.
• Experience improving system architecture, testing, and monitoring to ensure reliability and performance.
• A commitment to developing others; using code reviews, coaching, and shared best practices to help the team deliver its best work.
• Ability to collaborate cross-functionally with operations, product, and UX teams to ensure business value and user impact.
• A track record of designing platforms and customer experiences that will endure over years while remaining close to the details of execution.

Technologies We Use

• Backend: NET, .NET 10, ASP.NET Core, C#, Python
• Frontend: React, Typescript, JavaScript, CSS
• Database: MongoDB, Elasticsearch, SQL, Db2, Redis
• Testing: Selenium, Playwright, Xunit, Jest
• Infrastructure: Kubernetes, Jenkins, Gitlab, Azure, Linux, VMWare, IIS
• LLMs: OpenAI, Copilot, Claude, Gemini, Grok, perplexity, deepseek
• Applied AI: RAG, Embeddings, Vectorization, Machine Learning, Computer Vision
• Dev Tools: Swagger, Git
• Messaging /Data Streaming: Kafka, MQ

Cash Compensation

• Total cash compensation is generally around $235,000 to $310,000 and includes a profit sharing based on company profitability.
• You will also receive a relocation stipend (if applicable) and signing bonus.

Benefits

Growth & Learning

• 100% tuition reimbursement
• Informal and formal mentorship
• Employee resource groups

Health & Wellbeing

• Medical, dental, pharmacy, and vision plans with no monthly premiums
• Inclusive, all-gender benefits

Family & Future

• Paid parental leave for all new parents
• Adoption and surrogacy assistance
• First-time home buyer assistance
• Industry-leading company-funded retirement accounts

Time Off

• Paid vacation and personal time

Who You Are

We're looking for curious, driven engineers who thrive in collaborative environments and love solving hard problems. Ideal candidates will have:

• Experience designing and delivering large-scale, service-oriented systems.
• Strong proficiency in compiled languages such as C#, Java, C++, or Rust.
• A thoughtful, analytical approach to problem-solving and software design.
• Clear, confident communication skills across technical and non-technical audiences.
• Interest in mentoring, coaching, and growing as a leader.