About Rostyslav Zakroishchykov

Professional background

With more than 12 years of commercial experience, Rostyslav Zakroishchykov designs and delivers production backend systems: REST APIs, microservices, payment integrations, asynchronous workflows, and cloud infrastructure on AWS. Recent roles include AI Integration Engineer at Upwork and Backend Engineering Lead at Compass Mining, where work focused on RAG pipelines, payment gateway abstraction, and event-driven order processing with PostgreSQL and Celery.

Core strengths include retrieval-augmented generation, vector search, LLM prompt design, idempotent payment flows, webhook verification, database performance tuning, and refactoring legacy Node.js and Python codebases using SOLID and Clean Architecture principles.

Recent focus areas

• RAG systems: document ingestion, chunking, embeddings, vector retrieval, and context ranking
• AI document processing: OCR, preprocessing, LLM-based extraction, and structured JSON output
• Payment integrations: multi-gateway abstraction, Stripe/Plaid-style flows, reconciliation
• Event-driven architecture: Celery workers, lifecycle states, retries, and failure recovery
• API security: JWT auth, RBAC, rate limiting, Zod validation, and centralized error handling
• Performance: Redis caching tiers, SQL indexing, and high-traffic API optimization

Education

Bachelor's Degree in Information Technology at American University Kyiv (September 2022 – June 2026).

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