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Backend engineer

Tadej Slivnik

I design backend architectures that are dependable, modular, and ready to scale without sacrificing clarity — and I lean on AI agents to keep that standard while moving faster.

Client projects delivered
16 Client projects delivered
Led as lead developer
7 Led as lead developer
Owned as project architect
4 Owned as project architect
Shipping software
9 yrs Shipping software
Focus
Symfony · PHP · Python · AI-assisted engineering
Most recent
Lead Backend Developer, Creatim (2020–2025)
Education
Mathematics, University of Ljubljana
Get in touch LinkedIn

About Permalink to About

Core languages
PHP, TypeScript, Python.
Frameworks
Symfony, Drupal, Vue / Nuxt.
Data & Infra
MySQL, PostgreSQL, Elasticsearch, Linux.
Delivery & Ops
CI/CD pipelines, containerized services.
AI & agents
Claude Code, OpenAI Codex, MCP, agent orchestration.
Retrieval & search
Elasticsearch, embeddings, RAG pipelines.
Tooling
Git, VS Code, Webpack, Node.js, Postman.
Accessibility
Semantic HTML, WCAG adherence baked into components.

My Approach to Backend Systems

I build backend systems with a bias toward clarity, reliability, and long-term velocity. My approach is rooted in a few beliefs:

  • Simplicity scales — the cleanest design is usually the one that lasts.
  • Automation compounds — if a task is worth doing twice, it’s worth scripting once.
  • Tests are living documentation — they explain intent as much as they guard correctness.
  • Standards and accessibility matter — they reduce entropy and make systems friendlier for both humans and machines.
  • Agents are leverage, not autopilot — they earn their place when the guardrails (types, tests, contracts, review) are already in place.

What Quality Looks Like

Quality is not just about passing tests — it’s about creating systems that are predictable, easy to reason about, and a pleasure to evolve:

  1. Deterministic builds and deployments, with CI/CD as a policy gate.
  2. Architectures with sharp boundaries and domain language that lowers cognitive load.
  3. Shifting checks left — type safety, contracts, linting, security — so problems are caught early.
  4. Tooling that eliminates repetition, from templates to code mods.
  5. Evidence-driven performance — profile before tuning, respect latency budgets before chasing micro-optimizations.

Contributions

I’ve contributed to projects for organizations such as AMZS, Slovenia.info (including the Alma AI assistant), Domel, ZPS (Consumers Association), SloSki Accreditations, and Insurance company Vita. Across these, I’ve taken on roles ranging from hands-on developer to project architect and lead. The work has spanned complex content and data domains, personalization and recommendation systems, and performance-sensitive architectures where scalability and reliability were critical.

Projects Permalink to Projects

Selected client work delivered as developer, lead developer or project architect.

Guidelines Permalink to Guidelines

CI/CD
Continuous Integration & Continuous Deployment automation
DRY
Don't Repeat Yourself code reuse principle
GDPR
EU General Data Protection Regulation compliance
KISS
Keep It Simple, Stupid – minimize accidental complexity
OpenAPI
Machine-readable Application Programming Interface contract specification
OWASP
Open Web Application Security Project best practices / Top 10
REST
RESTful, resource‑oriented HTTP API design principles
Semantic HTML
Use proper elements (landmarks, headings, lists) to convey structure & meaning for a11y + SEO
SOAP
Simple Object Access Protocol XML-based messaging protocol
SOLID Principles
Five foundational Object-Oriented design principles
WCAG
W3C accessibility guidelines (POUR: Perceivable, Operable, Understandable, Robust)
YAGNI
You Aren't Gonna Need It – avoid premature features

Skills Permalink to Skills

Languages

  • PHP Primary language since 2020
    Expert
  • SQL Schema design, query tuning, migrations
    Expert
  • HTML Semantic markup, WCAG conformance
    Expert
  • JavaScript / TypeScript
    Advanced
  • Python Automation, data and AI tooling
    Advanced
  • C# Unity tooling and editor extensions
    Strong
  • CSS / SCSS
    Working
  • Java
    Working

Frameworks & platforms

  • Symfony Domain services, messenger, API platform
    Expert
  • Sylius E-commerce domain customisation
    Advanced
  • Vue.js
    Advanced
  • Drupal Custom modules, complex content models
    Strong
  • Nuxt
    Strong

AI & agentic engineering

  • Claude Code Agentic development: subagents, skills, hooks, MCP
    Expert
  • Agent orchestration Multi-agent pipelines, fan-out and verification loops
    Advanced
  • Context & prompt engineering Task decomposition, evaluation-driven iteration
    Advanced
  • OpenAI Codex Delegated implementation and review passes
    Advanced
  • Model Context Protocol Exposing internal systems as agent tools
    Advanced
  • Retrieval-augmented generation Embeddings, hybrid search, grounded answering
    Advanced
  • Structured output & tool calling Schema-constrained generation in production paths
    Advanced
  • LLM evaluation & guardrails Regression suites, cost and latency budgets
    Strong
  • GitHub Copilot
    Strong
  • Paperclip
    Strong

Architecture & delivery

  • API design REST, OpenAPI contracts, versioning
    Expert
  • Data modelling Relational design, indexing, query profiling
    Advanced
  • CI/CD pipelines Deterministic builds, quality gates on merge
    Advanced
  • Accessibility engineering WCAG built into components, not retrofitted
    Advanced
  • Search & indexing Elasticsearch mappings, relevance tuning
    Advanced
  • Containerised delivery Docker, reproducible environments
    Advanced
  • Caching & queues Redis, asynchronous workloads
    Strong
  • Observability Structured logging, tracing, incident follow-up
    Strong

Tools Permalink to Tools

AI & agents

  • Claude Code
  • OpenAI Codex
  • GitHub Copilot
  • Paperclip
  • MCP servers
  • LangChain
  • LLM APIs

Data & search

  • PostgreSQL
  • MySQL
  • MsSQL
  • MongoDB
  • Redis
  • Elasticsearch

Infrastructure & delivery

  • Docker
  • Linux
  • Nginx
  • Apache
  • Bash
  • GitHub Actions
  • GitLab CI
  • Windows

Developer tooling

  • Git
  • VS Code
  • Node.js
  • Vite
  • Webpack
  • Yarn
  • Postman
  • Figma
  • JSON
  • Unity

Working style Permalink to Working style

Adaptability
Ability to adjust to new conditions and changing requirements quickly and effectively.
Attention to Detail
Thoroughness in accomplishing tasks with precision and accuracy.
Collaboration
Working effectively with others to achieve common goals and outcomes.
Communication
Clearly conveying information and ideas through various channels.
Critical Thinking
Objective analysis and evaluation of issues to form a judgment.
Decision Making
Making timely, informed choices by evaluating options and their potential outcomes.
Mentoring
Providing guidance, feedback, and support to help others develop their skills.
Presentation Skills
Effectively communicating information to an audience in a clear and engaging manner.
Problem Solving
Identifying issues and implementing effective solutions.
Reliability
Consistently delivering on commitments and meeting expectations.
Team Leadership
Guiding and motivating a group toward achieving collective goals.
Work Ethic
Demonstrating dedication, discipline, and commitment to delivering quality work.

Career Permalink to Career

  1. Jun 2020 — Nov 2025

    Lead Backend Developer · Creatim

    Selected organisations & initiatives

    • AMZS
    • Slovenia.info, including the Alma AI assistant
    • SloSki Accreditations
    • Vita (insurance)
    • ZPS (Consumers Association)

    Core focus areas

    • Complex content and data domains
    • Personalisation and recommendation systems
    • Performance, scalability and reliability

    Role progression

    • Lead Backend Developer
    • Senior Backend Developer
    • Independent PHP Developer
    • Symfony
    • Drupal
    • PHP
    • Python
    • JavaScript
    • MySQL
    • PostgreSQL
    • Elasticsearch
    • CI/CD
    • WCAG
    • Vue.js

  2. 2016 — 2020

    Unity 3D Developer · Unity Asset Store

    Role

    VFX and shader developer building procedural, space-themed visual systems and the tooling around them.

    Published assets

    • Procedural Planets & Stars — animated celestial bodies
    • Starfield Shaders — optimised 2D and 3D starfields
    • Poly Planet Creator — stylised low-poly planetary generator

    Strengths

    • Procedural generation
    • Shader and VFX engineering
    • Performance optimisation
    • Tool design across realism and stylisation
    • Unity
    • C#
    • Shaders
    • GPU profiling
    • Editor tooling

  3. 2012 — 2018

    Faculty of Mathematics and Physics · University of Ljubljana

    Degree

    University Graduate in Mathematics

    Thesis

    König's Lemma and Kleene Tree

    Relevant coursework

    • Introduction to Programming (Python)
    • Programming 1 & 2 (Python, Java)
    • Numerical Methods & Linear Algebra
    • Data Structures & Algorithms
    • Optimisation
    • Database Fundamentals (SQL, R)

  4. 2008 — 2012

    Jesenice Gymnasium

    Programme

    General upper secondary education

Contact Permalink to Contact

Happy to talk about backend architecture, AI-assisted delivery, or a role you are hiring for.