Danylo

Danylo Senchyshyn
Full-Stack Developer · Java / Spring Boot · React / TypeScript · PostgreSQL
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SUMMARY
Full-stack developer with 3+ years of commercial experience building scalable backend systems and modern web interfaces.
Delivered features end-to-end across two commercial products in the CRM and arbitrage automation space. Strong focus on
distributed systems, performance, security, and clean testable code.

WORK EXPERIENCE
Full-Stack Developer — Softica SEP 2024 – Present · Remote

Enterprise task management platform with hierarchical workspaces, Kanban/Gantt/Calendar views, team collaboration, 2FA auth, and
role-based access control — built as a microservice system (backend, auth service, React/Next.js 15 frontend).

• Joined the project early and built the backend from the ground up — permissions, file uploads to S3, and core task workflow logic.
• Co-built a dedicated auth service with JWT and 2FA, handling authentication for the entire platform.
• Developed and maintained REST APIs with Spring Boot and Spring Security — optimized slow endpoints and improved
response times by up to 60%.
• Profiled queries with EXPLAIN ANALYZE, fixed N+1 problems, and introduced Redis caching — reduced DB load by ~40% and
improved key endpoint latency.
• Integrated RabbitMQ for async messaging between services, making the system more resilient to failures.
• Wrote unit and integration tests with JUnit and Mockito — reached ~70% coverage on core business logic; participated in code
reviews.
• Built Kanban board, Backlog, and Phases views from scratch — complex interactive UI with full task management functionality.
• Implemented task detail modals with comments, file attachments, custom selects, and custom calendar management — complete
feature ownership from design to API integration.
• Managed global state with Zustand and custom React hooks; REST API integration and responsive layouts with TailwindCSS.
Java Backend Developer — Softica MAR 2023 – AUG 2024 · Remote

CRM and arbitrage automation platform for Facebook traffic arbitrage teams — manages ad accounts, proxies, bots, channels, landing
pages, domains, flows, and aggregated Facebook advertising statistics across multi-tenant workspaces.

• Designed and implemented the core multi-tenant service — workspaces, users, bots, channels, lands, domains, and flows — with
Spring Boot 3.x / Java 21.
• Built REST APIs for Facebook ad account and proxy management, integrating with Python/FastAPI and Keitaro tracker via
OpenFeign.
• Implemented Facebook advertising statistics pipeline: raw SQL aggregation across campaigns/adsets/ads with Redis caching (10
min / 30-day TTL layers) — significantly reduced repeated DB load.
• Designed dual authentication: JWT Bearer (external token validation + local claim parsing) and API Key for service-to-service
calls.
• Integrated RabbitMQ topic exchanges for async event publishing (channel subscriptions, conversion events).
• Maintained ~70%+ test coverage with JUnit 5 + Mockito + mutation testing (PIT); wrote all Liquibase migrations.

TECH STACK
Backend: Java 17, Spring Boot, Spring MVC, Spring Security, Spring Data JPA, Hibernate
Frontend: React, TypeScript, JavaScript, TailwindCSS, HTML, CSS
APIs & Messaging: REST API, Microservices, Kafka, RabbitMQ, WebSocket, OpenAPI/Swagger
Databases: PostgreSQL, MongoDB, Redis, SQL, Liquibase/Flyway
Testing & QA: JUnit, Mockito, Postman, Integration Testing
DevOps & Tools: Docker, Git, Maven, GitLab CI/CD, Linux, Bash
Cloud: AWS (EC2, S3, RDS, IAM)
Cybersecurity: JWT, OAuth2, Spring Security
Architecture: MVC, Clean Architecture, SOLID, Design Patterns
Monitoring: Actuator, Prometheus, Grafana, ELK/Logback
AI Tools: Claude Code, AI Agents, OpenAI Codex
Project Mgmt: Jira, Agile/Scrum

PERSONAL PROJECTS

Banking Simulator — github.com/danylo-senchyshyn/banking-simulator

Production-grade microservices banking backend built as a deep-dive into distributed systems. Java 21 · Spring Boot · Apache Kafka ·
PostgreSQL ×4 · Redis · Spring Cloud Gateway · Resilience4j · OpenTelemetry · Testcontainers.

• Production-grade microservices banking system: auth, account, transaction, and fraud services with separate PostgreSQL
databases per service.
• Implemented distributed systems patterns: Outbox, DLQ, Circuit Breaker (Resilience4j), Idempotency via Redis, and Token
Hashing (SHA-256 refresh tokens).
• Async fraud pipeline via Apache Kafka; Spring Cloud Gateway with Redis-backed rate limiting; end-to-end distributed tracing
with OpenTelemetry + Jaeger.
• 123 tests (unit + @WebMvcTest + Testcontainers integration) with 0 failures; full observability stack: Prometheus + Grafana +
structured logs.
Job Scraper — github.com/danylo-senchyshyn/Job-Scraper

Multi-threaded job vacancy scraper for learning JSON API consumption, concurrency, and performance optimization.

• Multi-threaded job vacancy scraper using Java and HTTP API requests — up to 10× faster than the initial Selenium-based
prototype (also functional, but too slow for large datasets).
• Parses paginated JSON API responses across multiple job boards; supports concurrent fetching with thread pool, CSV/JSON export,
and keyword filtering.
Security Audit Log API — github.com/danylo-senchyshyn/security-audit-log

Security event logging and monitoring backend. Kotlin · Spring Boot · WebSocket/STOMP · JWT · PostgreSQL · Flyway · Docker.

• REST API with JWT auth and role-based access control (ANALYST / ADMIN) in Kotlin and Spring Boot 3.
• Real-time alert delivery via WebSocket (STOMP) — HIGH/CRITICAL severity events are broadcast instantly to all subscribers;
includes a browser-based live monitor.
• Spring Security filter chain with custom JwtAuthFilter; stateless auth, Flyway migrations, PostgreSQL, Swagger/OpenAPI docs.

EDUCATION
Technical University of Košice (TUKE)
Bachelor's degree in Computer Science · 2023 – 2026

Thesis: Comparative study of monolithic vs. microservice architecture (Java, Spring Boot, PostgreSQL, Apache Kafka). Performance
benchmarks with k6 showed the monolith achieved 14% higher throughput and 2.2× lower median latency; microservices provided better
fault isolation and independent deployability. Implemented the transactional outbox pattern and event-driven choreography.