This role modernizes legacy .NET applications and their data tiers onto supportable platforms. Most engagements start with a working-but-aging system — a .NET Framework 4.8 application backed by Oracle — and end with something maintainable, scalable, and testable on PostgreSQL RDS with Windows application servers on EC2. This is hands-on engineering with real constraints: production systems that can't go down, undocumented application logic, business logic buried in stored procedures nobody has read in a decade, and a migration that needs to be seamless and invisible to end users. Critically, this is not a database-only migration: the application layer itself must be modified to support PostgreSQL as the backend, not just have its data moved underneath it.
Requirements
What you will do
Assess existing .NET Framework applications — dependencies, integration points, data access patterns — and produce a realistic modernization plan with sequencing and risk called out.
Modify the application codebase itself to support PostgreSQL as the backend, beyond just migrating the underlying data.
Untangle and port data access layers, including legacy ADO.NET and older Entity Framework code, to current patterns.
Migrate database workloads from Oracle to PostgreSQL: schema conversion, PL/SQL to PL/pgSQL translation, data type and collation mismatches, query rewrites, and performance validation on the target.
Write the tests that make a migration defensible: characterization tests around legacy behaviour, integration tests across the data tier, and automated comparison of old vs. new outputs.
Work directly with client architects, DBAs, and product owners; explain trade-offs in plain language and document decisions so the next person understands them.
Contribute to CI/CD pipelines, deployment automation, and observability for the systems you migrate.
Mentor mid-level developers and review code with an eye on maintainability, not just correctness.
Required
10+ years of professional software development experience, with significant depth in C# and .NET.
Strong, current working knowledge of .NET Framework 4.8 and its legacy stack — ASP.NET MVC/Web API, Web Forms, WCF, IIS, and Windows Services.
Demonstrated experience modernizing or migrating existing applications — not just greenfield development.
Solid relational database skills: writing and tuning SQL, reading execution plans, understanding transaction and isolation behaviour.
Hands-on Oracle experience — PL/SQL, packages, procedures, triggers, sequences — enough to read and reason about business logic living in the database.
Experience with source control, branching strategy, and CI/CD in a team setting (Git, Azure DevOps, GitHub Actions, or similar).
Ability to communicate clearly with non-engineers and to work well when requirements are incomplete.
Engagement details
100% emote
Hourly, full-time commitment
2-month engagement with the possibility of extension
Open to candidates in Latin America
Highlights
Tech stack
C#, .NET Framework 4.8, ASP.NET MVC, Web API, Web Forms, WCF, IIS, Windows Services, Oracle PL/SQL, PostgreSQL, PL/pgSQL, SQL, Git, CI/CD (Azure DevOps / GitHub Actions), AWS (EC2, RDS)
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