Martin Rajniak – Senior Backend Software Engineer

Senior engineer with 12+ years building and shipping production systems. Recently built a full-stack LLM-powered application (Recall) using Kotlin Spring Boot on GCP Cloud Run, integrating PostgreSQL via Supabase and the Groq LLM API. Enterprise experience at Avast/Gen Digital (millions of users, cross-departmental scale), combined with hands-on ML and data-processing projects in Python. Comfortable owning backend systems end-to-end in small, fast-moving teams.

Backend Projects

Recall – Socratic AI Tutor IN PROGRESS

Kotlin Spring Boot REST API deployed to GCP Cloud Run
Supabase (PostgreSQL + Auth) for persistence and user management
Groq API integration for low-latency LLM inference
Socratic prompting system with multi-turn conversation state management
Book-specific grounding pipeline to constrain LLM output
Chrome extension for structured content extraction and ingestion
Compose Multiplatform client (Android + iOS) consuming the API

KotlinSpring BootGCP Cloud RunLLM APIPostgreSQL

Air Quality Prediction Pipeline

Large-scale time-series data ingestion, cleaning, and feature engineering
Multi-model comparison: ARIMA, Prophet, XGBoost, LSTM
Recursive multi-step forecasting with rolling-window cross-validation
CI/CD pipeline: GitHub Actions + Docker for reproducible builds

PythonXGBoostLSTMDockerGitHub Actions

Bean Disease Classification

Dockerized Modal cloud GPU training pipeline
Flask REST API for model serving with configurable hyperparameters
MLflow experiment tracking + Airflow workflow orchestration
End-to-end: data ingestion → training → API → mobile inference

PythonFlaskAirflowMLflowDocker

Technical Skills

Backend

Kotlin · Java
Spring Boot
REST APIs
Python · Go

GCP & Data

GCP Cloud Run
Firebase
Supabase PostgreSQL
BigQuery

AI & DevOps

LLM APIs
Docker
GitHub Actions
MLflow · Airflow

Engineering Background

iOS Senior Engineering Manager 2022–2024

Gen Digital (Avast) · Remote, Slovakia

Directed 4 mobile teams delivering strategic cross-functional solutions at scale
Drove cross-departmental CI/CD initiative to overcome post-merger integration barriers
Acted as domain expert supporting ML team in identifying suspicious releases

Principal / Lead Mobile Engineer 2015–2022

Avast Software · Prague, Czechia

Led Android + iOS teams building VPN client (millions of active users)
Applied Continuous Delivery to cut release cycles from bi-monthly to bi-weekly
Built and shipped Kotlin Multiplatform libraries in production iOS apps
Maintained client library for Google Play Billing System

Education & Learning

MSc Economic Informatics – Univ. of Economics, Bratislava 2007–2012

Hands-On ML – Scikit-Learn, Keras & TensorFlow (Géron) 2025

Developing Apps with Google Cloud – Coursera Specialisation 2024