Senior C# Architect

About the company:
One of our clients, based in Boston, USA, is a leading wellness technology company dedicated to helping organizations build healthier, more engaged, and productive workplaces.
The company offers customizable employee wellness programs designed to align with organizational culture, values, and business goals. Its solutions combine fitness technology, mobile applications, web-based tools, health content, and wellness services, including fitness classes, webinars, and health coaching.
The platform enables employees to track healthy habits, participate in wellness activities, earn rewards, and engage in friendly challenges. Through these solutions, the company helps organizations foster a stronger culture of health, well-being, and employee engagement.
About the Role:
We're looking for a Senior C# Architect to own the technical architecture of our core platform, spanning legacy in C#, ASP.NET, MVC/Web API, .NET Core services and modern cloud-native systems. You'll balance hands-on coding with high-level design, guide a team of engineers, and drive decisions on scalability, performance, and modernisation, including migration paths from .NET Framework to .NET 8+ version.
Key Responsibilities:
Own end-to-end architecture for C#, ASP.NET MVC and Web API applications, including API design, service boundaries, and data access patterns
Lead technical design reviews and set coding/architecture standards across teams
Drive cloud infrastructure decisions (AWS) compute, networking, storage, caching, and managed database services
Identify and resolve performance bottlenecks in production systems (SQL Server, IIS, connection pooling, caching layers)
Design and implement caching strategies (Redis/ElastiCache) to decouple read-heavy workloads from primary databases
Guide migration strategy from ASP.NET Framework (4.x) to .NET Core/.NET 8+, including hosting model changes (IIS to containerized/cloud-native)
Architect for high availability, disaster recovery, and horizontal scalability
Mentor senior/mid-level engineers on system design and code quality
Collaborate with product and infra teams to translate business requirements into scalable technical solutions
Own technical documentation, RFCs, and architecture decision records (ADRs)
Participate in incident response and root-cause analysis for critical production issues
Required Qualifications:
Deep expertise in C#, ASP.NET MVC, ASP.NET Web API (both .NET Framework and .NET Core/.NET 8+)
Strong background in RESTful API design, versioning, and security (OAuth2/JWT)
Proven experience architecting solutions on AWS (EC2, RDS, ElastiCache, Lambda, S3) equivalents
Solid SQL Server expertise: query optimization, indexing strategy, execution plan analysis, stored procedures
Experience with distributed caching (Redis) and message queuing (SQS, RabbitMQ)
Strong understanding of IIS configuration, application pools, and Windows Server hosting environments
Experience with CI/CD pipelines, containerization (Docker), and infrastructure-as-code (Terraform/CloudFormation)
Track record of leading legacy modernization/migration projects
Excellent communication skills able to explain architecture tradeoffs to both engineers and business stakeholders
Preferred Qualifications:
Experience with microservices architecture and event-driven design
Familiarity with Entity Framework/EF Core and ORM performance tuning
Exposure to mobile backend architecture (APNs, push notification systems, mobile API design)
Experience in health/wellness, fintech, or other regulated/data-sensitive industries
AWS/Azure architecture certification

Work arrangement
No