Senior .NET / C# Backend Developer
Multi-tenant SaaS — Migration Execution + Integrations
About Clearstone Software
Clearstone Software, LLC is a Texas-based technology company building two specialized platforms for the medical aesthetics industry:
Our Practice Management Platform — a mature, multi-tenant .NET SaaS for medical spas and clinics covering appointments, patient records (PHI), treatment planning, membership management, payments, and clinic operations. Currently running on .NET Framework 4.5-4.6 with a database-per-tenant multi-tenancy model, field-level PHI encryption, and HIPAA-aligned data-handling practices. Currently in final development for internal launch into our founder's own aesthetic clinics, followed by a coordinated stack modernization (to .NET 8/9 and ASP.NET Core) and infrastructure re-platform (Azure to AWS) ahead of commercial rollout to external med spa customers.
Our Practitioner Education Platform — a Laravel 10 + Filament 3 training and credentialing system for aesthetic practitioners, covering onboarding, skills assessment, competency monitoring, and continuing education. Built on a TALL stack (Tailwind + Alpine + Laravel + Livewire) with Vite for build tooling and AWS S3 for asset storage. Live video delivery is already integrated via Cloudflare Stream. Next phase: enterprise features, full multi-tenant SaaS launch, and AI-powered real-time practitioner feedback.
Our founder operates active medical aesthetic clinics under the Texas Lasers brand and leads a US-based aesthetic college and training institute. Every feature we ship gets tested in real clinical operations and real training environments before it reaches an external customer. We know what actually works in the aesthetic industry — not just what looks good in a demo — and that grounding shapes how we hire, how we prioritize, and how we ship.
Employment structure: All new hires begin employment via Multiplier Technologies Vietnam Company Limited (Employer of Record), with planned transition to direct employment with Clearstone Software Vietnam Co., Ltd. when we establish our Vietnamese entity in late 2026 / early 2027. This transition preserves continuity of service, social insurance, and all statutory benefits.
Work arrangement: Hybrid. You'll work 2-3 days per week from our team space in District 1 or District 3, Ho Chi Minh City, with the remaining days home-based. We value output over hours-in-chair; our office anchor days are for pair-programming, architecture discussions, and building the team.
The Role
You will be the primary backend engineer on our Med Spa Practice Management Platform, working alongside our .NET Modernization Lead and Frontend Modernization Engineer. Your focus is migration execution, integration work, and hardening — you'll be shipping the day-to-day port from legacy .NET Framework to .NET 8/9, moving Azure services to AWS equivalents, and maintaining PHI encryption and per-tenant isolation through every step.
You should be comfortable working across the full backend stack: EF6→EF Core migrations, Autofac→Microsoft DI refactoring, WebJobs→Lambda/EventBridge rewrites, Azure Service Bus→SQS/SNS/EventBridge porting. If you've done partial modernizations before and want to be part of a full end-to-end one, this role is designed for you.
What You'll Do
- Ship the tablet-based clinic check-in/checkout backend to complete internal launch on the legacy stack
- Execute project-by-project migrations from .NET Framework 4.5-4.6 to .NET 8/9 as the Lead sequences them
- Port ASP.NET MVC 5 / Web API 2 controllers and services to ASP.NET Core
- Migrate EF6 code-first data access to EF Core, preserving DB-per-tenant patterns
- Refactor Autofac 3 registrations to Microsoft.Extensions.DependencyInjection
- Port Azure WebJobs to AWS Lambda or ECS + EventBridge Scheduler
- Migrate Azure Blob to S3, Azure Service Bus / Queues to SQS/SNS/EventBridge, Azure Redis to ElastiCache
- Maintain and extend HIPAA field-level PHI encryption using AWS KMS
- Move secrets to AWS Secrets Manager
- Extend existing Authorize.Net payment integration; evaluate and integrate physical card-processing hardware
- Maintain existing Twilio (SMS) and SendGrid (email) integrations
- Migrate logging from log4net + Application Insights to Serilog + CloudWatch + OpenTelemetry
- Write and maintain xUnit/NUnit test coverage; raise coverage during migration
- Contribute to code reviews and architectural discussions
Required Experience
- 5+ years of professional C# / .NET development
- Hands-on experience with both modern .NET (.NET 6/7/8) AND legacy .NET Framework 4.x production code
- Real migration experience — you've participated in or led .NET Framework → .NET Core migrations, or ASP.NET MVC 5 → ASP.NET Core migrations
- Entity Framework 6 → EF Core migration experience
- Strong backend fundamentals: REST API design, dependency injection, async/await, Entity Framework
- Solid SQL Server production experience
- Proven API integration experience across payment providers, SMS providers, email providers, or cloud storage APIs
- Testing discipline as a default (xUnit, NUnit, or MSTest + Moq)
- Solid written English
Nice to Have
- Multi-tenant SaaS experience (subdomain-per-tenant, tenant resolution middleware, DB-per-tenant)
- HIPAA compliance implementation experience — even partial is a strong plus
- AWS production experience — ECS/Fargate, EKS, Lambda, S3, SQS/SNS/EventBridge, ElastiCache, RDS
- Autofac → Microsoft DI refactoring experience
- Authorize.Net, Stripe, or similar payment provider integration
- Twilio (SMS) or SendGrid (email) integration experience
- PDF/document generation tooling
- Docker containerization for .NET
What We Offer
- Salary: USD 3,000-4,200/month gross, paid monthly via Multiplier Technologies Vietnam (Employer of Record)
- 13th-month bonus (1 month of salary, customary in Vietnam, paid every December)
- Annual salary review with merit-based increases
- Full Vietnamese statutory benefits administered via EOR: social insurance, health insurance, unemployment insurance, occupational accident and disease insurance
- 12+ days annual paid leave per Vietnamese Labor Code, plus all Vietnamese public holidays, plus sick and personal leave per Vietnamese Labor Code
- Company-owned computer for your work
- Access to our team space at Dreamplex, District 1 or District 3, Ho Chi Minh City
- Company-provided VPN, MDM, security stack, and productivity software licenses
- Direct mentorship from the US-based founder
- Direct employment transition to Clearstone Software Vietnam Co., Ltd. planned for late 2026 / early 2027, with continuity of service preserved
Working Arrangement
- Hybrid: 2-3 days per week at our HCMC team space (District 1 or 3), remainder home-based
- Core overlap hours: 9:00 AM - 1:00 PM ICT for standup and synchronous work
- Output-based culture — we value what you ship, not hours-in-chair
- Initial 60-day probation via EOR, then indefinite-term contract
Application Process
- Sen your CV (PDF)
- Link to your GitHub profile or technical portfolio
- Short cover note (3 paragraphs max): why you're interested, a specific .NET Framework → .NET Core or EF6 → EF Core migration you've worked on, and your approach to maintaining production stability during coordinated migration work
- Earliest start date and current salary expectation in USD/month
Process timeline: ~3 weeks from application to offer.
