available for projects

.net/react.js fullstack developer

Ion Guzun

I build software for international clients that significantly improves their products and solves hard technical problems.

Senior .NET/React.js Fullstack developer with 5 years of experience — full-stack across Blazor and React.js, from low-level integrations to polished frontends. Worked in pharma, scientific instruments and transportation.

Start a project +373 61 081 052 LinkedIn
status.json
  • statusopen to freelance & B2B contracts
  • stack.NET / C# · React.js · Blazor
  • exp5 yrs · international clients
Portrait of Ion Guzun, senior .NET/React.js Fullstack developer
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about

Five years building software for international clients.

I'm a senior .NET/React.js Fullstack developer with 5 years of experience. I like building software for international clients — things that significantly improve their products and solve hard technical problems.

I've delivered greenfield platforms, modernized legacy systems and shipped full-stack applications end to end — from low-level device and binary-protocol integration to polished Blazor and React.js frontends.

I've worked across domains including pharma, scientific instruments and transportation, on platforms serving international brands.

Pharma & Batteryimaging · data
Scientific Instrumentsdevice · signal
Transport & LogisticsCRM · ops
Retail PaymentsPOS · fiscal
selected clients

Companies I've built for.

RTI Solutions RTi DENS Solutions DENS Alvys alvys

Worked on platforms serving international brands including Metro, L'Oréal and Adidas.

the toolbox

What I build with.

Deep in .NET / C# and Blazor, with strong React.js and TypeScript breadth and hands-on cloud, low-level and DevOps work.

Backend

.NET 10.NET Framework 4.7C# 14ASP.NET CoreLINQMediatRJWTCryptographyNode.jsExpress.jsPythonESC/POSLibUsbDotNetSerial / Binary

Frontend

React.jsBlazor.NET MAUI HybridWPF / XAMLSyncfusionTypeScriptJavaScriptNext.jsSciChartChart.jsFabric.js

Architecture & Data

DDDModular MonolithMicroservicesRESTgRPC / ProtobufEF CorePostgreSQLCosmos DBMongoDBSQLiteHDF5OpenCVNumPy / pandas

Cloud · DevOps · Testing

.NET AspireAzure Key VaultMicrosoft Entra IDAzure DevOpsDockerGitHub ActionsCI/CDNUnitMSTestMoqSwagger / Scalar
experience

Where I've made an impact.

Sep 2025 — May 2026 RTI Solutions Senior .NET/React.js Fullstack Developer

Enterprise Resource Management Platform

RTI Solutions was a big retail payment provider for Metro, L'Oréal and Adidas and wanted to scale their platform.

  • Integrated with a low-level POS fiscal payment system supporting 1000 devices at the same time.
  • Developed a whole greenfield application including a RESTful service served from an API Gateway using .NET 10 and C#.
  • Applied company-wide branding across the CRM by using Blazor and Syncfusion for the frontend across many modules.
.NET 10C# 14React.jsEF CoreDDDLINQREST APIMediatRFodyNuGetJWTCryptographyESC/POSLibUsbDotNetBinary protocolsBlazorSyncfusionAspireNUnitMSTestSwaggerMoqPostgreSQLAzure KV
May 2022 — Aug 2025 DENS Solutions .NET/React.js Fullstack Developer

Scientific Imaging & Analysis Platform

A pharma/battery research company in the Netherlands working in data analysis wanted to streamline their processes.

  • Improved the step-by-step analysis for image processing from an electron microscope for nano-meter accuracy, to image classification and data transformation from DM4 format.
  • Pre-processed images and transformed data into a proper unifying format using OpenCV for normalization, contrast and by creating a library of image filters.
  • Developed an export module for mp4 videos and for multiple image formats to help in scientific research and publications in scientific papers.
  • Streamlined the whole workflow from many fragmented tools into a single streamlined modern application using a modular monolith architecture based on .NET 8 and Blazor.
  • Extended application capabilities to enrich the UI by developing an annotation filter for a time period which also displays charts besides the video using the SciChart library.
  • Made the system robust by migrating .NET 6 to 8 and by writing unit tests using Moq, NUnit and C#.
  • Improved application security by integrating with Azure Active Directory (AD).
.NET 8C# 12React.js.NET Framework 4.7Python 3MVVMgRPCProtobufOAuthLINQJWTXAMLBlazor.NET MAUITypeScriptSciChartFabric.jsHDF5OpenCVNumPyPandasGitHub ActionsNUnitMoqAzure AD
Oct 2020 — Apr 2022 Alvys .NET / Blazor Fullstack Developer

Transport & Logistics CRM

  • Improved managers overview by implementing the accidents, claims and maintenance modules using .NET Core.
  • Extended the UI/UX components to make it easier for dispatchers and drivers to be more intuitive and efficient.
  • Increased the stability of the CRM by being involved, prompt and eager to resolve issues.
  • Contributed to migration from ASP.NET to ASP.NET Core and added unit tests using NUnit for the core modules.
  • Collaborated well with the cross-functional team across 30 developers from different departments.
C# 10ASP.NET Web APIASP.NET CoreMVCLINQREST APINUnitMoqBlazorJSONMailchimpCosmos DBAzure DevOps
on the side

Built outside the day job.

R&D startup2025

R&D Company Portal

A company portal for a research & development startup, built with Next.js.

Private startup2020

News Feed Portal

A CNN-style news feed portal for a private startup, built with React.js.

background

Education & track record.

BSc in Informatics Lucian Blaga University · Sibiu2020
1st place — Regional Olympiad in Informatics2017
3rd place — National Olympiad in Informatics2016
Top 30 — Kangourou National Math Competition2016

Languages

Romaniannative
Englishadvanced
let's talk

Have a hard problem worth solving?

I take on freelance and B2B contracts. Tell me about your product or problem — I'll tell you, honestly, how I'd approach it.

[email protected] Connect on LinkedIn
tel · +373 61 081 052 git · github.com/guzunj loc · Chișinău · Remote