Portfolio · 2008 to Today

Dejan
Petković

AI engineeringFullstack · Cloud

That’s me. Hi.

Intro

I started my career as a system engineer back in 2008, and over the years built up deep fullstack engineering experience across React, Node.js, Python, and cloud platforms. That hands-on breadth is what I now bring to AI engineering as the founder of Elands AI.

Amsterdam canal with houseboats, brick houses and bare winter trees

Amsterdam · NL · 52.37° N

§ 01 · About

I build the whole product.

Bio

I started my career as a system engineer back in 2008, and over the years built up deep fullstack engineering experience across React, Node.js, Python, and cloud platforms. That hands-on breadth is what I now bring to AI engineering as the founder of Elands AI, where we design and deliver intelligent systems for startups and small companies.

As a Dutch citizen and fluent speaker of English, Dutch and Serbian, I have worked extensively with Dutch 🇳🇱, American 🇺🇸 and British 🇬🇧 customers.

Building with generative AI is no longer just a learning interest: it is my day job. Through Elands AI, I design and ship LLM-based applications, evaluation infrastructure, and real-time AI services for clients. You can browse some of my experiments on GitHub, including agentic usage with MCP servers.

I spend my free time with family, learning Dutch, exploring emerging technologies and taking care of my health via balanced diet and strength training.

And as a Dutchman, I ride kids to school in our Urban Arrow bakfiets (cargobike), so fun and gezellig 🎉 (joyful in Dutch).

Experience

Since 2008

System engineer to AI engineer

Languages

EN · NL · SR · DE · RU

Companies

From Liberty Global to Delphyr

§ 02 · Projects & Services

Things I have built.

Selected · 2017 to 2026

01 · FeaturedAI for the medical field

Delphyr

delphyr.ai

A next-gen AI platform built specifically for the medical field. I founded the engineering effort behind it and led it through its first year. We are bringing AI into real clinical workflows, from hospitals to GP practices, without compromising on usability, privacy, or compliance. I now focus on the AI layer: prompt design, safety and grounding evaluation, and the observability that keeps model behavior measurable in production.

Visit Delphyr

Role

Lead

Founded the eng. effort

Stack

Py / TS

FastAPI · Kubernetes

Focus

AI layer

Prompts · safety · obs.

What I built

· Adversarial guardrail evaluation suite

· Jailbreak & prompt-extraction testing

· Prompt design & grounding for ambient clinical documentation

· Per-specialism templates & transcript-level verification

· Evaluation harness & release gating on regressions

· LangWatch observability & PHI-safe tracing

02SaaS · Finance

Biller

biller.elands.studio

Professional invoicing for freelancers. Create, send, and track invoices in seconds. One-time purchase, no subscriptions.

Visit Biller

03Civic · Dutch market

Bouwen

bouwen.elands.studio

Renovation project communication for the Dutch market. Print a QR code for your window and let neighbours follow your renovation in real time.

Visit Bouwen

04Tax · Calculator

2e-woning.nl

Box 3 tax calculator: easily calculate your tax for a second home and other investments. Built for the Dutch market.

Visit 2e-woning.nl

05LLM · WhatsApp · MCP

brAIn

github.com/dexpetkovic/brAIn

WhatsApp-based AI assistant built with NestJS and Google Gemini. Handles WhatsApp webhook events and generates contextual replies, with an MCP server that lets the model store, update and retrieve memories.

View on GitHub

§ 03 · Skills

The toolbox.

AI and LLM Systems

LLM APIs (OpenAI-compatible)Azure MLNebiusGoogle GeminiMCP serversAgentic tool usePydantic AIpydantic-evalsPrompt design & groundingLLM-as-judge evaluationGuardrails & adversarial testingLangWatchPHI de-identification (Deduce)

Programming Languages

PythonTypeScriptScalaJava

Frameworks and Libraries

FastAPINext.jsPydanticSQLAlchemy / AlembicPostgreSQLNode.js / NestJSKafkaSpark / DatabricksFlinkpandasReactReact NativeTailwindCSSPlaywrightJest

Platforms and Infrastructure

AWSAzureKubernetesDockerArgoCDTerraformGitHub ActionsOpenTelemetryPrometheus / GrafanaSentry

Spoken Languages

English · FluentDutch · Fluent (NT2)Serbian · FluentGerman · IntermediateRussian · Intermediate

§ 04 · Experience

Since 2008, compounded.

NowOngoingActive

Founder & AI Engineer

Elands AI

Elands AI designs and delivers intelligent systems for startups and small companies. Building with generative AI is no longer just a learning interest: it is my day job.

Designing and shipping LLM-based applications for clients
Building evaluation infrastructure for LLM systems
Building real-time AI services

2025Jun 2025 to PresentActive

Lead AI Engineer

Delphyr B.V. · AI for the medical field

I founded the engineering effort behind a next-gen AI platform built specifically for the medical field, and led it through its first year. We are bringing AI into real clinical workflows, from hospitals to GP practices, without compromising on usability, privacy, or compliance. I now focus on the AI layer: prompt design, safety and grounding evaluation, and the observability that keeps model behavior measurable in production. I work mainly in Python and FastAPI, across the Kubernetes and TypeScript surfaces around it.

Architecting and building the adversarial guardrail evaluation suite our safety layer is graded against: jailbreaks, prompt extraction, medical misinformation, balanced against safe controls
Owning prompt design and grounding for ambient clinical documentation, from per-specialism templates to transcript-level verification of every generated statement
Building production-grade LLM systems: from evaluation harness and release gating on measured regressions to LangWatch observability and PHI-safe tracing

2024Sep 2024 to Jun 2025

Expert Software Engineer

Totally Gifts · Greenfield gift card platform

Development of a greenfield project with a new tech stack, from scratch.

Next.js, TailwindCSS, Clerk, Sentry, NestJS, PostgreSQL, Docker and AWS used to build the solution
Event-driven architecture to capture gift card events and process them in real time
Contributed across the stack with a cross-functional team of three engineers, a designer, and a product owner
Management of App Store and Play Store releases

2023Nov 2023 to Sep 2024

Lead Fullstack Software Engineer

Grndhouse · On-demand strength training

Team lead managing a team of 5 backend and frontend developers on grndhouse.com, a platform for on-demand strength training.

Led the development of the initial MVP after a successful funding round
Took regular meetings with stakeholders to streamline delivery of video streaming, payment processing, and user management features
Architected and implemented features using React Native, Node.js and AWS
Mentored junior developers, resolved blockers, and ensured timely project delivery
Tooling: Sentry for event monitoring, RevenueCat for payments, Mixpanel for analytics
Expo to manage app lifecycle and deployments, with or without App Store / Play Store releases

2021Dec 2021 to Nov 2023

Fullstack Software Engineer

Fertifa · Reproductive healthcare

Progressed from individual contributor to team lead, managing a team of 5 backend and frontend developers on fertifa.com, Europe's most comprehensive reproductive healthcare provider.

Defined and developed features in collaboration with the product owner and stakeholders
Engineered solutions in React Native, Node.js and AWS
Mentored junior developers and led sprints to ensure timely delivery
Tooling: Strapi for content management, Sentry for monitoring, Google Analytics, Meta Pixel, Drip and Amplitude for analytics
Manual app lifecycle management and deployments

2018Jun 2018 to Dec 2021

Senior Software Engineer

KPN Technium B.V.

Senior engineer in the team developing an ETL automation framework and platform in Azure, based on the Hadoop & Kafka ecosystem, automated by Terraform.

Rendering framework built with Python, Flask and SQLAlchemy
Led story mapping for migration of on-premise data platform services to Azure
Development of a distributed event-sourcing application for real-time analysis of the KPN customer journey, where multiple touch points are combined, analysed and visualised
Scala stack with Akka / Alpakka used to build microservices and Flink applications
DevOps methodology with fully automated CI/CD, monitoring and alerting

2017Feb 2017 to May 2018

Software Engineer, Cognitive Implementation

IPsoft B.V. · Amelia AI framework

As technical lead of a 3-member agile team I was responsible for development of human-machine interaction on the artificial intelligence framework Amelia.

Mostly hands-on development, code reviewing, mentoring and Scrum rituals
Development mostly in Groovy / Python and in Java
Stack: Kafka · Camel · Mule · Elasticsearch · Spring · Grails · Docker
Data analysis with Pandas and Jupyter, visualisation with d3.js, and making new feature (or refactoring) decisions from the insights

2012Jun 2012 to Jan 2017

Senior System Engineer

Liberty Global B.V. · OTT streaming

As member of Liberty Global's OTT streaming solution architecture & engineering team, I worked on the architecture of various system components, developing AWS (micro)services infrastructure, CDN content delivery, Adobe AEM and their integration.

Microservices development in Python
Deep knowledge of web and backend application design, streaming technologies, HA scalable infrastructure, AWS cloud and full stack network protocols, acquired through work with high availability services
Data analysis with Jupyter, Wireshark, Conviva and Omniture
Performing code reviews and overall system troubleshooting

§ 05 · Education

Where it started.

2009Sep 2009 to Feb 2011

Masters Course: System Engineering and Radio Communications

Faculty of Electrical Engineering, University of Belgrade

Specialization: Telecommunications and software engineering

2002Oct 2002 to Aug 2007

BSc of Electrical Engineering