Senior Software Engineer · Backend Architecture · Enterprise .NET Systems

Halil İbrahim Sayın

I build production-grade .NET systems and open source the patterns that survive enterprise scrutiny. Based in Ankara, working at the intersection of legacy modernization and AI tooling.

About

Six-plus years building .NET systems across regulated industries — energy market integrations, DO-178C avionics, MIL-STD-1553B helicopter control systems, large-scale enterprise platforms, and AR training simulators. Currently Senior Software Engineer at Enerjisa, owning the production .NET stack behind Turkey's electricity market (EPİAŞ, TEİAŞ, TPYS, CPS) — high-volume data ingest from millions of meter readings, audit-grade logging, and Hangfire-based background pipelines that reduced manual workload by ~50%.

My current focus is the intersection of AI coding tools and enterprise .NET. Most public content treats Claude Code and similar tools as hobbyist toys. I'm interested in what they look like inside an audit-grade codebase — what skills, playbooks, and rules actually survive a compliance review. I open source that work.

Experience

Dec 2024 — Present

Senior Software Engineer · Enerjisa

Own the production .NET stack behind Turkey's electricity market integrations — designing EDW services that ingest millions of meter readings under strict regulatory data submission deadlines. Built Hangfire-orchestrated background pipelines that automated daily TEİAŞ submissions for three companies, cutting manual workload by ~50%. Drove observability across the stack with Graylog, reducing production incident detection time.

.NET 8 React Vue.js PostgreSQL SQL Server Oracle Hangfire Graylog

Aug 2023 — Dec 2024

Senior Software Engineer · Koç Sistem

Led the end-to-end digitization of a corporate recruitment platform, designing data integrity-focused candidate and manager modules under Agile/Scrum cycles. Architected EF Core + MSSQL data access patterns that scaled across business workflows, cutting manual recruitment operations workload by ~30% and shipping iterative releases on Azure.

.NET MVC Entity Framework MSSQL Azure Agile

Feb 2022 — Aug 2023

Software Engineer · Havelsan

Built real-time C++ systems certified to DO-178C safety-critical avionics standards. Worked across GIS-POSIX and GIS-ARINC653 RTOS specifications, balancing certification rigor with the agility needed to deliver airborne software on tight verification cycles.

C++ DO-178C RTOS GIS-POSIX GIS-ARINC653 .NET Core

Feb 2021 — Feb 2022

Avionics Software Engineer · Aselsan

Engineered MIL-STD-1553B-compliant data communication infrastructure for Turkish indigenous helicopter control systems. Designed safety-critical data flows in C++ using IBM Rhapsody, managing requirements and configuration traceability across military development standards.

C++ MIL-STD-1553B IBM Rhapsody JIRA ClearQuest

Nov 2019 — Feb 2021

Software Engineer · Başarsoft

Served as integration lead on .NET Core desktop and web applications backed by MSSQL and Oracle. Designed GIS integration layers with OpenLayers and GeoServer over REST APIs, coordinating data flow across geospatial subsystems in production environments.

.NET Core MSSQL Oracle OpenLayers GeoServer REST API

Nov 2017 — Nov 2019

Software Engineer · Bites Defence & Aerospace

Developed augmented reality training simulators for defense applications using Unity and Vuforia. Built C/C++ tracking systems with Qt and multi-threaded Linux messaging on .NET Core, integrating disparate hardware and software stacks into interactive training environments.

Unity Vuforia C/C++ Qt .NET Core AR

Selected Work

Open Source · Released on NuGet

ef-migration-safety

A .NET CLI tool that statically analyzes EF Core migration files and flags destructive operations, missing defaults, empty Down() methods, and unsafe rename operations before they reach production. Built with Roslyn; distributed as a global dotnet tool on NuGet.

.NET 8 Roslyn CLI Static Analysis NuGet

Open Source · Active

claude-code-for-dotnet

A production-grade collection of skills, playbooks, and CLAUDE.md templates for shipping enterprise .NET code with Claude Code — designed around the patterns that survive audit and compliance review in regulated environments. Covers structured logging architecture, EF Core migration safety reviews, and legacy .NET modernization playbooks. Maintained as a living document.

Claude Code .NET 8 EF Core Serilog xUnit

Side Project · AI + Astrology

ZephryAstro

A full-stack AI-augmented astrology platform combining classical natal chart computation (SwissEphNet) with structured content generation pipelines. Architected the .NET 8 backend, React frontend, and Python content automation layers — shipping daily Turkish-language content across Instagram and X, with a long-term aim of a paid natal and solar return reporting platform.

.NET 8 React SwissEphNet Python Pillow

Case Study · Energy Sector

Oracle to PostgreSQL Migration

Architected and executed the migration of a multi-million-row enterprise dataset from a legacy Oracle deployment to PostgreSQL — rewriting Oracle-specific PL/SQL into PostgreSQL equivalents, restructuring schema patterns, and validating data integrity across the cutover window. Preserved query semantics and reporting pipeline performance while reducing licensing costs.

Oracle PostgreSQL PL/SQL T-SQL .NET 8 EF Core

Case study available on request

Writing

Long-form essays on .NET production engineering, Claude Code workflows, and the gap between AI coding tool demos and what actually ships under audit pressure. First essays publishing throughout 2026.

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What I Build With

Languages  — C#, TypeScript, Python, SQL
.NET  — ASP.NET Core, EF Core, Serilog, xUnit, Hangfire
Frontend  — React, Vue.js, Astro, Tailwind CSS
Data  — PostgreSQL, MSSQL, Oracle, Redis
Infrastructure  — Docker, GitHub Actions, Azure
AI Tooling  — Claude Code, Claude API, MCP

Get in Touch

Open to consulting on enterprise .NET modernization, production AI tooling adoption, and migrations.