Sr. C# Developer, SaaS Platform Architecture

Sr. C# Developer, SaaS Platform Architecture
*** DO NOT APPLY IF YOU DO NOT HAVE*****
Master's Degree in Computer Science or related
SaaS architecture ---------- authentication and authorization, permissions & role design.
.Net Security & Clean Architecture.
Solid knowledge ---------- , EF
Solid concept of relationship databases & db design.

Must Have:
---------- , C#, ---------- (Core/5+), not just Framework; ASP.NET Core Web API: middleware pipeline, DI container, configuration/options pattern, hosted services; Async/await done right. Knows why .Result deadlocks, understands cancellation tokens, IAsyncEnumerable; EF Core at depth: change tracking, query translation vs client eval, migrations, split queries, AsNoTracking, and knowing when to drop to raw SQL or Dapper instead

Multi-tenancy
Has shipped a real multi-tenant SaaS product, not just read about it
Can articulate tradeoffs across the isolation models: shared schema with tenant discriminator, schema-per-tenant, database-per-tenant. Should have opinions on migration pain and noisy-neighbor risk
Tenant resolution strategies (subdomain, header, claim) and how tenant context flows through the request pipeline
Enforcement at the data layer, not just at the controller. EF Core global query filters, and understanding of why filters alone are not sufficient (raw SQL paths, background jobs with no HTTP context)
Per-tenant configuration, feature flags, and connection routing
Tenant-aware caching. Knows how cache key collisions become data leaks

Auth and authorization
OAuth 2.0 and OIDC beyond copy-paste: authorization code + PKCE, client credentials, token lifetimes, refresh rotation, why implicit flow is dead
JWT validation internals: signature, issuer, audience, clock skew, key rotation via JWKS
BFF pattern experience. Cookie-based session at the edge, token exchange behind it
ASP.NET Core authorization model: policies, requirements, handlers, resource-based auth. Should prefer policies over scattered role checks
RBAC vs ABAC, and permission modeling that survives a customer asking for custom roles
Identity provider integration experience (Entra ID, Auth0, Duende IdentityServer, Keycloak)
Data and SQL Server
Strong T-SQL: CTEs, window functions, stored procedures, table-valued functions
Execution plan reading, index design, and diagnosing the usual suspects (parameter sniffing, implicit conversion, N+1)
Row-level security awareness as a defense-in-depth layer for tenancy
Security
Parameterized queries as reflex. Can spot injection risk in a dynamic query builder during review
OWASP Top 10 working knowledge, secrets management, CORS, CSRF in cookie-based flows
Architecture and delivery
Clean/layered architecture, dependency inversion, and enough taste to not over-abstract
API versioning, consistent error contracts (RFC 7807 / ProblemDetails), correct HTTP semantics
Testing: unit, integration with WebApplicationFactory and Testcontainers or LocalDB. Multi-tenant isolation tests specifically
CI/CD with Azure DevOps or equivalent, branching strategy opinions, code review discipline
Observability: structured logging with tenant correlation, distributed tracing, health checks

Nice to have
YARP or another reverse proxy in production
Redis for distributed cache and session
Azure: App Service, Key Vault, Service Bus, Azure SQL elastic pools
Background job frameworks (Hangfire, Quartz) with tenant context propagation
Front-end literacy in React/TypeScript, enough to review a PR and design a sane API contract
Legacy migration experience (Delphi, VB6, .NET Framework to Core)
Domain-driven design, event sourcing, or workflow engines (Elsa, Flowable)
Mini Orange experience
Soft requirements
Writes architecture decision records and can defend a decision without getting defensive
Comfortable owning a slice end to end in a small team, no hand-holding
Mentors through code review rather than rewriting other people's PRs