Alex Batten, Freelance .NET & Full-Stack Engineer in Denmark

Last updated: August 17, 2026

Hi, I'm Alex, a software engineer in Denmark with a BEng in Software Technology from DTU. Most of my work is C# and .NET: backend services, REST APIs, and enterprise integrations, with full-stack web on top. I publish three .NET libraries on NuGet under the Invarix name. Outside work I train and produce music.

Not available for new work right now. Email alex.batten1234@gmail.com and I will say when that changes.

Experience

Senior Software Engineer, AI Infrastructure at Alignerr (Contract, signed 2026, not yet started)

Signed contract, first assignment still pending. The agreed scope is the infrastructure behind AI training, evaluation, and deployment pipelines, in Python and TypeScript.

Stack: Python, TypeScript.

Backend Developer at Acconta (2026–Present)

Designed and shipped production microservices on a multi-tenant SaaS platform (.NET Aspire, ASP.NET Core, EF Core), each taken from prototype to deployed service with OpenAPI/NSwag generated typed clients. Owned Stripe billing end to end: subscriptions and seat logic (proration, credits, plan switching, yearly plans, webhooks, secret hardening), plus a working subscription flow prototype in the Next.js client. Implemented Danish tax compliance: VAT reporting to SKAT via the NemVirksomhed service (SOAP with WS-Security signing), computing all 17 VAT return fields, plus SAF-T import with schema validation. Also built standalone integrations for daily currency rates (National Bank) and company data via CVR (Danish Business Authority).

Stack: C#, .NET Aspire, ASP.NET Core, Entity Framework, Microservices, Stripe, Next.js.

Generalist Expert, AI Evaluation at Mercor (Contract, 2026–Present)

Evaluating AI model outputs against structured evaluation guidelines and writing the rationale behind every judgment. The work is close reading: checking a response for factual accuracy, sound reasoning, instruction following, and tone, then stating precisely where it holds up and where it breaks down, with evidence. Applying the same standard consistently across a wide range of subject areas so that assessments stay comparable between reviewers.

Skills: AI Evaluation, LLM Outputs, Structured Feedback, Technical Writing.

AI Data Annotator at Outlier (2025–Present)

Contributed to advanced AI model development through data annotation, prompt engineering, trajectory refinement, and QA across projects including Clutch Zayu, Maraca Camera, Mechanic Astrologer, and Meter Pavilion (OpenClaw). Crafted system prompts defining model behavior and constraints, and designed single and multi-turn conversational and agentic datasets spanning 50+ risk categories including bias, misinformation, privacy, and safety. Built autonomous agent trajectories exercising skill discovery, memory, long-horizon context, and native tools (cron, sub-agent delegation). Served as both author and reviewer on Mechanic Astrologer.

Skills: AI/ML, Prompt Engineering, Agentic AI, Data Annotation.

Software Development Intern at IT Operators / Simple Agency Group (2024)

Developed REST APIs with auth, rate limiting, and monitoring. Built fullstack web apps with Angular, .NET, and Bootstrap, including JWT auth, real-time dashboards, and automated reporting. Migrated an in-house ERP's time representation from quarter hours to minutes across every display, estimate and report field, then rebuilt the billing review on top of it so a task worked by employees from more than one group billed under each of those groups instead of one. Validated the rebuilt invoicing screen by reconciling a full month of billing data against what had actually been invoiced.

Projects

Professional work at IT Operators / Simple Agency Group

Accelo to Business Central integration (Bachelor Project)

Fullstack application bridging two enterprise platforms, transferring and reviewing time registrations from Accelo (PSA) into Microsoft Business Central (ERP). Built a custom UI for reviewing and adjusting hours before syncing. Designed the data model in MSSQL, implemented multi-tenant authentication via Microsoft Entra ID, and containerized the entire stack with Docker in a Jenkins CI/CD pipeline. Fully tested, with unit tests on both layers plus integration tests using Selenium and WebApplicationFactory.

Custom REST API for Uno X (Client: ISTOBAL)

Custom API for ISTOBAL (car wash manufacturer) serving operational data to Uno X (Nordic fuel station chain), with a custom token-based authentication system and rate limiting with automated email alerts on threshold breach.

Automated SMS alert system (Client: Eye4u)

Extended a customer monitoring portal with automated SMS notifications triggered by medicine cooler temperature deviations across a sensor network. Added an adjustable pre-alarm tier that warns by SMS and email without raising an incident, with suppression logic so a sensor sitting outside its threshold does not re-notify on every check. Built as a multi-tenant module, each customer with their own sensor configuration and alert thresholds.

Internal portal (Client: Dexa Bodyscan)

Built the initial web application for a body-scan clinic's internal portal, from an empty repository to a working authenticated application in eight working days: project scaffold, Dockerfile, DNS record, SSL certificate, MySQL schema, Entity Framework contexts, JWT login, salted password hashing, role-gated pages, and password reset from an email link.

Internal Monitoring Dashboards (IT Operators)

Real-time dashboards deployed on Raspberry Pis for office TV screens, monitoring time registrations and cron job health to track work efficiency and catch failed jobs early.

External API integrations (Client: TIMEVAT)

Integrated the EU VIES API for VAT number validation and the Danish National Bank API for daily currency exchange rates into a VAT compliance platform.

Personal projects

Invarix Guard

A plug-and-play AI safety library for .NET, shipped as a NuGet package (Invarix.Guard). Covers several AI safety categories out of the box, including prompt injection, PII, and content safety, so apps can add guardrails in a few lines of code. Website: invarix.dk. NuGet: nuget.org/packages/Invarix.Guard.

Invarix Guard Evidence

A free .NET library (Invarix.Guard.Evidence), licensed under Elastic License 2.0, that records AI decisions as an append-only audit trail. Each decision is stored as a CloudEvents event keyed on SHA-256 hashes rather than the prompt text. Batches are sealed into an RFC 6962 Merkle tree and signed with the customer's own Ed25519 key, so an auditor can prove no record changed after sealing using standard Certificate Transparency tooling. Includes retention with legal holds, signed deletion certificates, and a streaming export endpoint. Runs fully in process with no outbound calls. Website: invarix.dk. NuGet: nuget.org/packages/Invarix.Guard.Evidence.

Invarix Gate

A deterministic action firewall for AI agents, shipped as a NuGet package (Invarix.Gate). It sits in front of an agent's tool calls and evaluates each one against a policy before it runs, returning allow, warn, escalate, deny, or terminate. Ten detectors cover destructive SQL, shell commands, git history rewrites, cloud teardown, credential egress, and runaway loops, each grounded in a dated public incident. Matching is pure CPU pattern work with no model call, so a verdict lands in a median of 57 µs and is deterministic under a given policy. Policy is authored in YAML or fluent C#, attaches through Microsoft.Extensions.AI and Microsoft Agent Framework, and reports the surfaces it cannot see rather than rendering a clean run. Ships with a 194 scenario policy corpus where roughly half the cases assert a detector stays quiet. Observe mode is free under Elastic License 2.0. Website: invarix.dk. NuGet: nuget.org/packages/Invarix.Gate.

Hemi-Sync Guided Meditation App (paused)

A concept app for generating customizable guided meditations using AI-driven text-to-speech layered with Hemi-Sync binaural beat technology for brainwave entrainment. Built in React Native targeting both iOS and Android.

Distortion VST Plugin

An audio distortion plugin with bitcrushing built with the JUCE framework (C++), compatible with most DAWs as a VST. GitHub.

Skills & Tools

Languages: C#, C++, Java, TypeScript, JavaScript, Kotlin, SQL.

Frameworks & Libraries: ASP.NET Core, Entity Framework, Angular, .NET, .NET Aspire, Next.js, React Native, Bootstrap, JUCE.

Concepts & Practices: REST APIs, System Design, Distributed Systems, Agile/Scrum, CI/CD, JWT Auth, Docker.

Other: Git, Claude Code, ERP Systems, Multi-tenant SaaS, SAF-T, Audio Engineering.

Education

BEng Software Technology, Technical University of Denmark (DTU), 2021–2025

Electives in Computer Graphics, Rendering, C++ Programming, and Engineering Economics. Bachelor's project: an integration between two ERP systems built from scratch. GPA: 7.62 (Danish 7-point scale).

Recommendations

Mike Valencia, CEO at Simple Agency Group

Wrote about Alex Batten’s work at Simple Agency Group. View the post on LinkedIn.

Erik Seifert

Endorsed Alex Batten for C#, .NET Framework, and Entity Framework (EF) Core.

Frequently Asked Questions

Is Alex Batten available for freelance or contract work?

Not right now. I am not taking on new freelance or contract work at the moment. Email alex.batten1234@gmail.com and I will say when that changes. The work I take is .NET and full-stack web applications, REST APIs, enterprise integrations, and AI features, remote across the EU on CET.

Where is Alex Batten based, and does he work remotely?

Alex Batten is based in Denmark and works remotely across the EU on Central European Time. He speaks English and Danish.

What is Alex Batten's main tech stack?

Primarily C# and .NET, including ASP.NET Core, .NET Aspire, and Entity Framework Core. On the frontend, Angular, Next.js, and TypeScript. He also works in C++, Java, Kotlin, and SQL, with Docker, CI/CD, REST API design, distributed systems, and multi-tenant SaaS.

What kinds of projects does Alex Batten take on?

.NET backend and full-stack web applications, REST API design, integrations between enterprise systems such as ERP, PSA, accounting, and tax-authority platforms, multi-tenant SaaS features, and AI/ML features including guardrails and evaluation.

Does Alex Batten have experience with Danish tax and accounting integrations?

Yes. At Acconta he implemented VAT reporting to SKAT through the NemVirksomhed service (SOAP with WS-Security signing), computing all 17 VAT return fields, plus SAF-T import with schema validation. He has also built integrations for CVR company data from the Danish Business Authority, daily currency rates from the Danish National Bank, and the EU VIES API for VAT number validation.

Has Alex Batten worked with Stripe billing?

Yes. He owned Stripe billing end to end at Acconta: subscriptions and seat logic covering proration, credits, plan switching, and yearly plans, along with webhooks, secret hardening, and a working subscription flow prototype in the Next.js client.

What AI and machine learning experience does Alex Batten have?

The Alignerr contract is signed and the first assignment is still pending. The agreed scope is the infrastructure behind AI training, evaluation, and deployment pipelines. AI evaluation for Mercor, assessing model outputs against structured guidelines. Data annotation, prompt engineering, and agentic trajectory design for Outlier across 50+ risk categories. He also publishes three AI-related .NET libraries: Invarix.Guard, Invarix.Guard.Evidence, and Invarix.Gate.

What software has Alex Batten published?

Three NuGet packages. Invarix.Guard is a plug-and-play AI safety library for .NET covering prompt injection, PII, and content safety. Invarix.Guard.Evidence is a tamper-evident audit trail for AI decisions that records them as CloudEvents keyed on SHA-256 hashes and seals batches into an RFC 6962 Merkle tree signed with the customer's own Ed25519 key. Invarix.Gate is a deterministic action firewall for AI agents that evaluates tool calls against a policy before they run, with ten incident-grounded detectors and no model call.

What is Alex Batten's education?

A BEng in Software Technology from the Technical University of Denmark (DTU), 2021 to 2025, with electives in Computer Graphics, Rendering, C++ Programming, and Engineering Economics. His bachelor's project was an integration between two ERP systems built from scratch. GPA: 7.62 on the Danish 7-point scale.

How do you get in touch with Alex Batten?

By email at alex.batten1234@gmail.com, or by sending a project brief through the request form at alexbatten.dk, which also has live chat. He is on GitHub at github.com/AlexBatten and on LinkedIn. Project requests get a reply within a couple of days.

Contact

Email: alex.batten1234@gmail.com.
GitHub: github.com/AlexBatten.
LinkedIn: Alex Batten.