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I will fix or build your asp net core web API
Nikola R
About this gig
Most of my work is on .NET APIs that already exist. Something broke, it got slow, or it needs a new feature and the person who wrote it is gone.
I've written C# for over six years. Right now I work on a large .NET 10 system (Kafka, SQL Server, Cassandra) where a lost message means lost data, so I pay attention to logging, retries and tests.
What I can do:
- find and fix bugs in ASP.NET Core APIs: 500 errors, wrong data, slow queries, auth problems
- add endpoints and features in the style your code already uses
- connect a third-party API or webhook (payments, CRM, email)
- build a new REST API with EF Core or Dapper, Swagger and tests
- upgrade an older project to .NET 10
How I work: first I reproduce the problem, then I fix it on a separate branch and write you a short note on what was wrong and what I changed. You get the code as a pull request or a zip.
Please message me before ordering. A short description and an error message or screenshot are enough for me to tell you which package fits, or to send a custom offer.
Get to know Nikola R
Nikola R
Senior backend developer, APIs and n8n automation
- FromSerbia
- Member sinceOct 2026
Languages
English, Serbian
I've been writing C# for over six years, mostly on the backend. Right now I work on a smart-metering platform: .NET 10 services that talk over Kafka, with SQL Server and Cassandra behind them. Before that I built Azure backend services for a tax platform, and spent four years on a logistics company's TMS, ERP and CRM (ASP.NET Core, Angular, SQL Server). I started in 2018 in application support.
On Fiverr I take on API work, bug fixes in existing .NET apps, integrations and n8n automations. I find the cause before I change code, and I explain what I changed in plain words.
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FAQ
Can you work on my existing code?
Yes, that's most of what I do. I need access to the repository (GitHub, GitLab, Azure DevOps or a zip) and a way to run it, ideally with a test database.
Which .NET versions do you work with?
.NET Framework 4.x up to .NET 10. An older project can be upgraded, but first I tell you what the upgrade involves.
What do I get at the end?
The code as a branch, pull request or zip, plus a short note on what changed and why. If deployment is part of the job, I deploy it or write down the steps.
What if the job turns out bigger than the package?
I tell you before I go past the package and send a custom offer for the rest. I don't charge for anything we haven't agreed on.
Can we talk before I order?
Yes. I'm in Central European Time and reply within a few hours.
