Senior Software Engineer

Position Type: Contract with chance for conversion to full-time employment
Compensation: $100,000–$150,000, depending on experience
Location: St. Louis, MO
Schedule: Hybrid, generally 9:00 AM–5:00 PM. On-site expectations will be discussed directly with selected candidates and the employer.

Company: The name of our partner organization will be disclosed to candidates selected to move forward in the interview process. This is an opportunity through LaunchCode working with one of our company partners.

Role Purpose & Scope

The Senior Software Engineer is responsible for designing, developing, and deploying the core services that carry the heaviest logic and highest load on the platform. You will work on pricing and eligibility services at the core of the product. This is a deep backend position on the current Microsoft stack, covering C#, modern .NET, and Azure. This role has no front-end component.

The systems you will own are rules-driven and computationally demanding. They handle large volumes of complex, interdependent business logic where correctness is critical and where a poorly chosen data structure or unnecessary allocation can create noticeable latency. The work is well suited for engineers who genuinely enjoy reading profiler traces, reasoning about algorithmic complexity, restructuring hot paths, and determining which design pattern fits a particular problem rather than defaulting to a familiar approach.

Analytical depth is equally important. Much of the difficulty is not simply writing code, but understanding intricate business rules well enough to model them cleanly, identifying where new rules conflict with existing ones, and reasoning about how a change propagates through a system with many interacting conditions. This role is suited for someone who enjoys decomposing genuinely complicated problems and is comfortable taking ownership of technically consequential decisions.

The team also invests seriously in AI-assisted development and treats it as an engineering practice rather than an experiment. You will work alongside AI tooling with an emphasis on improving the quality of what is delivered, not simply development speed. You should be able to work independently with little supervision, influence architecture decisions, and lead technical initiatives across the team.

How We Work

Written clarity matters more here than in many engineering roles. Engineers are expected to think through a problem and document their approach before building it.

You are accountable for everything that merges under your name. AI tooling can produce significant amounts of plausible-looking code quickly, and the person submitting that code owns whether it is correct. Getting a change verified matters as much as building it. Tests and documentation are part of delivering work, not follow-up tasks. Sensitive parts of the system always receive human review regardless of what an automated check says.

The team is also transparent about the mix of work. A meaningful portion of its capacity goes toward extending and supporting systems that are already live, not solely new development.

Role Responsibilities

• Design, develop, and maintain the backend services at the center of the platform using C#, modern .NET, and ASP.NET Core.

• Own the performance characteristics of the code you write. Profile, measure, and optimize for latency, throughput, memory allocation, and database efficiency rather than relying on assumptions.

• Apply design patterns and architectural approaches deliberately and be able to explain why a particular pattern fits the problem and which alternatives were rejected.

• Model complex business logic in a way that remains maintainable as rules accumulate and identify where new requirements conflict with existing behavior before they are built.

• Design and implement cloud-based solutions on Microsoft Azure using compute, data, caching, and messaging services appropriate to the workload.

• Document an implementation approach before building, including the components expected to change, edge cases, testing approach, and how the change can be reversed if necessary.

• Produce test evidence, identify the potential blast radius of changes, and provide sufficient handoff details for QA to verify changes effectively.

• Work with AI-assisted development tooling as part of your normal workflow and develop the judgment to recognize where it adds value and where it should not be trusted.

• Review code carefully, including code written by others and AI-generated code. Confirm that completed work matches agreed-upon requirements and reject work that does not reconcile.

• Take ownership of scalability, reliability, and security through sound engineering practices rather than after-the-fact fixes.

• Troubleshoot and resolve complex technical issues in production systems, including problems that emerge only under real-world data volumes and concurrency.

• Mentor and guide other developers and contribute to raising the technical standards of the team.

• Stay current with the Microsoft ecosystem and advocate for technologies and practices that provide meaningful value.

• Collaborate with Product, QA, and other engineers throughout the software development lifecycle, from planning and design through testing and deployment.

Key Performance Indicators

Within the first 90 days: Deliver meaningful changes to complex logic without close supervision and clearly explain the performance implications of the solutions you build.

Within the first year: Become a trusted reviewer for some of the most complex areas of the codebase, measurably improve the performance or maintainability of areas you own, and become a resource other engineers rely on when addressing particularly difficult technical problems.

Qualifications & Skills

• Substantial professional software development experience with a strong focus on the Microsoft technology stack. Demonstrated capability, technical depth, and problem-solving ability are more important than meeting a specific years-of-experience threshold.

• Bachelor's degree in Computer Science, Software Engineering, or a related field, or equivalent practical experience.

Technical Skills

• Deep proficiency in C# and modern .NET, including asynchronous programming, concurrency, and memory behavior. Candidates should understand how the runtime operates, not simply how to produce compiling code.

• Demonstrated experience with application performance engineering, including profiling and benchmarking, identifying and resolving bottlenecks, reasoning about algorithmic complexity, and reducing allocation and query overhead in code operating at scale.

• Strong command of design patterns, domain modeling, and separation of concerns, with the judgment to determine when a pattern adds meaningful value and when it adds unnecessary complexity.

• Substantial experience with ASP.NET Core and RESTful API design and implementation.

• Strong SQL Server skills covering schema design, indexing, and query performance tuning, including the ability to interpret execution plans.

• Proven experience with Microsoft Azure, including compute, managed data services, caching, and Azure DevOps.

• Experience with build and release automation, automated testing, and infrastructure as code.

• Experience working within a large existing codebase where changes may have implications beyond the immediate area being modified.

Analytical & Professional Skills

• Exceptional analytical ability with the capacity to take dense or ambiguous business rules, identify the underlying structure, and translate them into clean, testable solutions.

• Ability to gather and interpret data to support technical decisions rather than relying solely on preference.

• Ability to document complex business logic clearly enough for others to understand and maintain.

• Excellent problem-solving skills and strong attention to detail.

• Strong verbal and written communication skills.

• Ability to make sound decisions under pressure and work independently while contributing effectively within a team.

• Strong organizational and time management skills with a proactive approach to learning.

Desired Skills

• Experience with high-throughput, low-latency, or calculation-intensive systems.

• Experience with distributed caching, messaging, and event-driven patterns.

• Previous exposure to AI coding assistants within a professional codebase. This is a plus rather than a requirement, and the team will invest in developing these skills for candidates who are curious and rigorous about their use.

• Experience with test-driven development and automated testing approaches beyond basic unit testing, including property-based or invariant testing for calculation-heavy logic.

• Experience with cloud-native deployment and containerization.

• Experience in financial services or another regulated industry is a plus.

Competencies & Technology Stack

• Backend: C#, modern .NET, ASP.NET Core, Entity Framework Core, LINQ

• Database: SQL Server

• Cloud: Microsoft Azure

• DevOps: Azure DevOps, source control, build and release automation

• Engineering Focus: Performance optimization, domain modeling, scalability, reliability, and complex business logic

• AI-Assisted Development: AI development tooling supported by established engineering practices and documentation standards