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Matthaios Ioannidis

@matthaiosioannidis

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Senior .NET developer specializing in scalable backend systems and cloud-native APIs.

Greece

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What I'm looking for

I seek senior backend or cloud roles where I can design scalable APIs, improve reliability through testing and automation, mentor teams, and drive measurable delivery and performance improvements.

I am a senior backend engineer with extensive experience designing and implementing scalable, high-performance APIs and services using .NET Core, Java EE and Python. I have delivered production systems for payments, betting platforms and telecoms, led testing practices to maintain >90% coverage, and improved delivery through automation, containerization and CI/CD.

I collaborate closely with product, frontend, DevOps and QA, have acted as Scrum Master to accelerate releases, and hold multiple Azure and cloud-related certifications. I focus on maintainable code, measurable quality improvements, and pragmatic solutions that reduce defects and operational risk.

Experience

Work history, roles, and key accomplishments

Senior Backend Engineer

Sitecore

Jun 2023 - Sep 2025 (2 years 3 months)

Designed and optimized .NET Core RESTful APIs backed by Azure Cosmos DB to enable scalable, high-performance data access; implemented xUnit/NSubstitute test suites to maintain >90% coverage and reduced defects by 30% through code reviews and best practices.

C++.NET Core Azure Cosmos RESTful APIs xUnit NSubstitute API Design Agile Scrum

Software Engineer

Intralot

Aug 2020 - Jun 2023 (2 years 10 months)

Built and maintained lottery and sports betting platforms using .NET Core, Java EE and Python; implemented Redis caching for low-latency real-time data and developed React/Redux agent apps, improving operational efficiency.

.NET Core Java EE Python Redis React Redux Docker CI CD BASH

Backend Developer

Viva Payments

Oct 2019 - Jun 2020 (8 months)

Built backend services for payments (card schemes, IBANs, bill payments) using .NET and SQL Server and implemented Refit-based REST APIs to integrate new payment schemas with comprehensive NUnit/Moq tests.

C++.NET SQL Server REST APIs NUnit Moq Integration Testing

Software Engineer

Nokia Hellas Technology Center

Jun 2016 - Oct 2019 (3 years 4 months)

Developed .NET Framework web tools and ASP.NET Web API 2 services for LTE/4G network documentation, improving publishing efficiency by 20% and aligning outputs with global Nokia standards.

C++.NET Framework ASP.NET Web API 2 CMS (Vasont)Python Troubleshooting

Network Support Engineer

Nokia Hellas Technology Center

Dec 2014 - Jun 2016 (1 year 6 months)

Supported In-Service Upgrades for LTE networks, debugging element servers and resolving production issues using Python automation and log analysis to perform root-cause investigations.

Python LTE Debugging Log Analysis Root Cause Analysis Customer Collaboration

Education

Degrees, certifications, and relevant coursework

University of Piraeus

Master's Degree, Advanced Information Systems

Master's Degree in Advanced Information Systems completed in February 2018 with a thesis on prediction of financial time series.

Technological Educational Institute of Athens

Bachelor's Degree, Electronic Engineering

Bachelor's Degree in Electronic Engineering completed in June 2013 with a thesis on design and implementation of telecommunication designs on FPGA chip.