Bilal Köse
Senior Software Engineer | .NET · Kubernetes · Microservices · Distributed Systems
Professional Summary
The code I write processes millions of transactions every day — reliably, at scale, and without compromise. With 10+ years of experience across fintech, e-invoicing, and digital infrastructure, I design systems that power critical operations for thousands of enterprise clients. I've cut processing latency by 60%, reduced production errors by 45%, and led platform migrations for services handling over 2 million daily requests. I take full ownership of what I build — from architecture to production, from the first commit to the last alert.
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
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 |
Professional Experience
Senior Software Engineer
–
Teamsystem · Mikrogrup
2024 – Present
- Engineer on Turkey's largest e-invoice platform processing 500K+ documents/day, 2M+ API requests/day, 2K+ msg/sec peak (RabbitMQ), with 99.9% uptime SLA serving 15K+ enterprise clients
- Architected event-driven microservices (RabbitMQ + MassTransit) across 5+ high-traffic services; improved P99 API latency from ~350ms → <200ms through async pipeline redesign
- Reduced incident resolution time by ~40% by implementing request tracing (X-Request-ID) and centralized observability via Graylog
- Accelerated release cadence by contributing to Kubernetes-based GitOps pipelines (Jenkins, ArgoCD) 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 Engineer
–
Team.Blue · Natro
2022 – 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)
- 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
2020 – 2022
- Reduced system latency by ~25% and improved operational efficiency by ~35% on a real-time video 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
Full-Stack Developer
–
Pardus Software
2018 – 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
- Implemented reliable background job processing pipelines with Hangfire for scheduled tasks, automated notifications, and batch data operations across multiple concurrent client projects
- Progressed from web developer to independent freelance engineer within 12 months — independently scoping, building, and delivering .NET solutions for diverse business requirements
Key Projects
Self-Hosted Kubernetes Production Lab
2023 – Present
- Designed and self-manage a bare-metal Kubernetes cluster running 12+ production-grade services on personal infrastructure, publicly accessible via custom subdomains
- Services include: GitLab (CI/CD), SonarQube (code quality), ArgoCD (GitOps), Rancher (cluster management), Jenkins (automation), Graylog (log aggregation), RabbitMQ (messaging), NuGet (package registry), File Server — all under bilalkose.com.tr
- Demonstrates end-to-end DevOps ownership: provisioning, networking, TLS, monitoring, and continuous delivery — fully self-managed outside of working hours
Kubernetes
ArgoCD
GitLab CI
Rancher
Graylog
RabbitMQ
SonarQube
Jenkins
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
Natro — Domain & Hosting Platform Modernization (10+ Services)
2022 – 2024
- Migrated 10+ mission-critical VB.NET services — domain activation, hosting provisioning, payment processing, customer management, renewal workflows — to .NET 7 for Turkey's #1 hosting platform serving 300K+ customers and 800K+ domains with 99.9% uptime SLA
- Reduced production error rates by ~45%, improved API response times by ~30%, and cut incident detection time by ~50% across all migrated services
- Expanded structured logging across entire service layer; integrated Sentry for real-time alerting, enabling proactive issue resolution before customer impact
.NET 7
ASP.NET Core
MSSQL
Sentry
Octapull — Real-Time Video Collaboration Platform
2020 – 2022
- Reduced latency by ~25% and improved operational efficiency by ~35% on a platform supporting 1,000+ concurrent users
- Validated 100-participant simultaneous sessions with screen sharing, enabling production-scale deployment
Jitsi Meet
.NET (C#)
ASP.NET MVC
JavaScript
Docker
GitLab CI
Graylog
Education & Certifications
Bachelor of Engineering, Computer Engineering
Karabuk University
CKA — Certified Kubernetes Administrator In Progress
Cloud Native Computing Foundation (CNCF)