Requirements:
4+ years of experience in Machine Learning, Recommendation Systems, or Applied AI
Experience building recommendation algorithms in production environments
Strong understanding of ML fundamentals and mathematical concepts
Experience training and evaluating recommendation models
Ability to work independently and take ownership of core product systems
Fluent English

Skills:
Recommendation systems
Ranking algorithms
Feature engineering and feature extraction
User personalization systems
Two-tower architectures
Neural networks and activation functions
LLMs and prompting systems
Python and ML tooling
Data-driven experimentation and optimization

Nice to Have:
Experience working on social media recommendation systems
Experience building large-scale personalization engines
Startup experience
Experience with consumer-facing products
Experience in gaming, entertainment, or content discovery products

What We Offer:
Salary range: €6,000-€8,500 net/month
Meaningful equity package
Founding team opportunity
Direct impact on product direction and company success
Work with AI-native gaming products
Fast-moving startup environment
Opportunity to relocate to Sofia and work closely with founders

Recruitment Process:
Technical interview with founders
Culture fit interview
Technical presentation / case study discussion
Final decision

Benefits
Salary range: €6,000-€8,500 net/month
Meaningful equity package
Founding team opportunity
Direct impact on product direction and company success
Work with AI-native gaming products
Fast-moving startup environment
Opportunity to relocate to Sofia and work closely with founders

Green Flags
Experience at companies with strong B2C feed-based recommendation systems (e.g., TikTok, Meta, Spotify, YouTube, Pinterest).
Experience at top-tier European e-commerce or marketplace companies with sophisticated personalization (e.g., Allegro, Zalando, Booking.com, Vinted).
Has shipped a 0-to-1 recommendation system from scratch in a startup environment.
Previously a founder or very early-stage employee.
Experience within the Bulgarian iGaming sector (e.g., EGT, Playtech) is considered a strong local talent pool.
Red Flags
Candidates unwilling or unable to work on-site 5 days/week in Sofia, Bulgaria.
Non-fluent English speakers.
Candidates with purely academic or research backgrounds without production ML experience.
Lacks a fundamental understanding of ML mathematics (e.g., cannot explain activation functions, network architectures).
Salary expectations significantly above the stated €72K-102K annual range.
Experience is exclusively in large, slow-moving enterprise environments with no startup or fast-paced product exposure.

If you are selected, you will receive an email inviting you to schedule a screening interview. from techtree