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Bilal Köse

Computer Engineer  |  .NET  ·  Kubernetes  ·  Microservices  ·  Distributed Systems
Kocaeli, Turkey [email protected] linkedin.com/in/bilalkse gitlab.bilalkose.com.tr bilalkose.com
Professional Summary

Senior Software Engineer with 10+ years of hands-on experience across backend platforms, distributed systems, e-invoicing and cloud infrastructure. I design, build and operate production services, mainly in the .NET ecosystem and also with Java/Spring Boot and Flutter, with a focus on reliability, maintainability and performance. Outside my full-time role, I independently develop and publish GlamUp Girls, a multilingual mobile game on Google Play and the App Store.

Core Competencies
Backend Architecture & System Design Microservices & Event-Driven Systems High-Throughput API Development Performance Optimization & Reliability CI/CD & GitOps Pipelines Kubernetes Administration (Self-Hosted) Distributed Systems & Messaging Technical Leadership & Mentorship Legacy Modernization Observability & Incident Response E-Invoice & Financial Document Processing AI-Assisted Engineering
Technical Skills
Backend .NET, C#, ASP.NET Core, Web API, Entity Framework Core, Java, Spring Boot
Architecture Microservices, Event-Driven Architecture, CQRS, Clean Architecture, SOLID, Domain-Driven Design
Data & Messaging MS SQL Server, Redis, RabbitMQ, Kafka, MassTransit
DevOps & Cloud Docker, Kubernetes, GitLab CI, Jenkins, ArgoCD, Rancher, Azure, AWS
Observability Graylog, Sentry, SonarQube, OpenTelemetry, Centralized Logging
Security PKCS#11 HSM, XAdES, PAdES, KamuSM compliance
Mobile Flutter, Dart, Firebase (Firestore, Cloud Functions, Remote Config, Crashlytics)
Professional Experience
Senior Software Engineer  –  TeamSystem / Mikrogrup · Istanbul, Türkiye · Remote Jun 2024 – Present
  • Backend engineer on a large-scale e-invoicing platform serving enterprise clients
  • Build event-driven microservices with RabbitMQ and MassTransit across high-traffic services; improved API latency through an asynchronous pipeline redesign
  • Implemented end-to-end request tracing (X-Request-ID) and centralized observability with Graylog, shortening incident resolution
  • Contribute to Kubernetes-based GitOps deployments (Argo CD, Jenkins) across production environments
  • Led cross-service architecture reviews and established resilient error-handling and observability standards — patterns adopted as the team's engineering baseline across all production services
Senior Software Developer  –  team.blue · Natro Jul 2022 – Jan 2024
  • Engineered backend services for Turkey's #1 domain & hosting platform — part of Team.Blue group (2.5M+ customers, 22 countries) — managing 800K+ domains, serving 300K+ customers, and processing 5K+ daily transactions (activations, renewals, payments) under a 99.9% uptime SLA
  • Reduced production error rates by ~45% and improved API response times by ~30% by leading full-stack migration of 10+ legacy VB.NET services — covering domain activation, hosting provisioning, payment processing, and customer management — to .NET 7
  • Expanded structured logging coverage across all migrated services, enabling end-to-end request tracing and cutting incident detection time by ~50% via Sentry integration
  • Optimized MSSQL performance through indexing and query refactoring, reducing average query execution time across high-traffic provisioning services
  • Established migration patterns and code standards adopted as the team's architecture baseline for all subsequent modernization projects
Software Engineer  –  MayaICT Aug 2020 – Jul 2022
  • Reduced system latency by ~25% and improved operational efficiency by ~35% on Octapull, a real-time video collaboration platform supporting 1,000+ concurrent users
  • Validated 100-participant simultaneous video sessions with screen sharing under production load, enabling full-scale deployment
  • Built and shipped scheduling, session management, and tracking modules across the full stack (.NET + JavaScript), integrating directly with Jitsi Meet-based video infrastructure under high-concurrency production load
Freelance Web Developer  –  Pardus Bilgisayar Yazılım Dec 2019 – Aug 2020
  • Designed and shipped full-stack web applications using ASP.NET Core, MVC, and MySQL for SME clients — owning architecture, database schema, business logic, and production deployment end-to-end
  • Independently scoped, built and delivered .NET solutions for diverse business requirements
Web Developer  –  Pardus Bilgisayar Dec 2018 – Dec 2019
  • Implemented reliable background job processing with Hangfire for scheduled tasks, automated notifications and batch data operations
  • Developed web applications and internal tools with .NET and MySQL, focusing on backend development and database design
Selected Projects
GlamUp Girls — Mobile Dress-Up Game · Independent Developer & Owner Apr 2026 – Present
  • Independently develop and publish a multilingual mobile dress-up game on Google Play and the App Store (EN/TR/AR), operated through my registered sole proprietorship in Türkiye; developed outside my full-time role.
  • 14 playable characters, 1,000+ outfits, accessories, hairstyles and makeup options and 4 pet packs; style duels, community voting, weekly and monthly competitions, and 28-day seasons
  • Flutter client on a Firebase backend (Firestore, Cloud Functions, Remote Config, Crashlytics); in-app purchases validated server-side for both stores; AdMob ads
  • Turkish, English and Arabic; automated tests include layout-overflow checks at multiple screen sizes
Flutter Dart Firebase Cloud Functions In-App Purchases AdMob
Self-Hosted Kubernetes Production Lab 2023 – Present
  • Designed and self-manage a bare-metal Kubernetes cluster on personal infrastructure running 20+ services, most of them delivered through GitOps as ArgoCD applications synced from Git; web-facing services are exposed on custom subdomains
  • Services include: GitLab and GitLab Runner (CI/CD), Jenkins (automation), ArgoCD (GitOps), Renovate (dependency updates), SonarQube (code quality), Rancher (cluster management), Prometheus and Grafana (monitoring), Graylog (log aggregation), RabbitMQ (messaging), NuGet feed — all under bilalkose.com.tr
  • Demonstrates end-to-end DevOps ownership: provisioning, networking, TLS, monitoring, and continuous delivery — fully self-managed
Kubernetes ArgoCD GitLab CI Rancher Graylog RabbitMQ SonarQube Jenkins Prometheus Grafana
HSM-Signer Service — PDF/XML Digital Signing Platform 2025
  • Reduced signing latency by 60% (800ms → 300ms) by redesigning the request processing pipeline for a PKCS#11-backed HSM platform
  • Increased throughput by ~60% by introducing asynchronous queue-based architecture handling 10K+ daily signing/verification operations
  • Reduced incident resolution time by ~40% via end-to-end request tracing (X-Request-ID) across all API operations
  • Delivered XML (XAdES) and PDF (PAdES) signing with KamuSM-compliant secure key management; containerized with Docker for high-availability deployment
Java Spring Boot Docker PKCS#11 REST APIs
Education & Certifications
Bachelor of Engineering, Computer Engineering
Karabuk University
2021
CKA — Certified Kubernetes Administrator In Progress
Cloud Native Computing Foundation (CNCF)
2025