Senior Backend Developer with 13+ years of experience building high-load systems serving millions of users. Currently leading search infrastructure at Superjob (8M+ monthly users), specializing in ML integration and microservices architecture.
PROVEN TRACK RECORD
At Superjob (2024-Present):
- Implemented ML-powered search ranking using CatBoost via CGO, achieving >15% CTR improvement with 4ms inference time for 8M monthly users
- Led migration from Sphinx to Manticore Search for multi-million resume database, implementing real-time indexing via binlog replication
- Built complete MLOps pipeline processing terabyte-scale ClickHouse datasets
- Developing semantic search service using PyTorch embeddings with expected 20-30% relevance improvement
At Manychat (2019-2022):
- Led strategic Instagram API integration during closed beta for 40+ developers and 3M+ users
- Refactored critical template cloning component, reducing processing time by >30% and memory consumption by 80%
- Achieved >75% test coverage, identified and fixed 50+ critical bugs
TECHNICAL EXPERTISE
Languages: Go (Expert), PHP (Expert), Python (Advanced), JavaScript/TypeScript, Lua, Bash
Databases: PostgreSQL, MySQL, ClickHouse, Redis, Qdrant, Manticore, Elasticsearch, Firebird
Infrastructure: Kubernetes, Docker, CI/CD (GitLab, GitHub Actions, ArgoCD)
Message Systems: RabbitMQ (Expert), Apache Kafka, Redis Pub/Sub
Search & ML: Manticore (Expert), CatBoost, PyTorch, Hugging Face Transformers
Monitoring: Prometheus, Grafana, Jaeger, Loki
SERVICES OFFERED
1. Search Infrastructure Design and Optimization
- Migration from legacy systems (Sphinx, Elasticsearch)
- ML-powered ranking implementation
- Real-time indexing solutions
2. Microservices Architecture
- Event-driven systems with RabbitMQ/Kafka
- API design (REST, gRPC, WebSockets)
- Service mesh implementation
3. ML/AI Integration
- End-to-end MLOps pipelines
- Model deployment and A/B testing
- Vector search implementation
4. Performance Optimization
- Database query optimization
- Caching strategies
- Load testing and profiling
5. Legacy System Modernization
- Migration from monoliths to microservices
- Technology stack upgrades
- Zero-downtime migrations
ENGINEERING APPROACH
I combine deep technical expertise with business impact focus. My solutions prioritize measurable outcomes - whether it's improving CTR, reducing latency, or cutting operational costs. Experience ranges from startups to platforms serving millions of users.
All deliverables include comprehensive documentation, monitoring setup, and knowledge transfer. I maintain ownership mentality for every project, ensuring long-term success beyond initial implementation.
Available for both long-term engagements and project-based consulting. Remote collaboration experience across multiple time zones.
GitHub: github.com/krajcik
LinkedIn: linkedin.com/in/krajcik