Mykhailo

Mykhailo Haida Java Engineer
Ternopil, Ukraine [open contact info](look above in the "contact info" section) t.me/ThisIsNotMyNickname

[open contact info](look above in the "contact info" section) [open contact info](look above in the "contact info" section)

SUMMARY
Java Engineer with 2+ years building B2B SaaS and MedTech systems on Spring Boot. Delivered domain-oriented
microservices, REST/WebSocket/Kafka pipelines, multi-tenant RBAC/PBAC security, and GDPR/HIPAA-ready
auditability. Strong in PostgreSQL tuning, integrations (S3, ML), and CI/CD with Docker + GitHub Actions.

CORE SKILLS
Java, Spring Boot, JPA/Hibernate, Maven/Gradle, Lombok
Microservices, DDD-lite, REST APIs, gRPC, SOAP, DTO/Mappers, Service/Repository layering
Spring Cloud: Eureka, OpenFeign, Spring Cloud LoadBalancer
PostgreSQL (indexes, JOIN tuning, partitioning), MongoDB, Redis caching
Kafka, WebSockets, async messaging, buffering, back-pressure, retries
Security: JWT, HTTP-only cookies, Keycloak, RBAC/ABAC/PBAC, 2FA, audit logging
AWS S3, external REST integrations, SMS/Email providers, Python ML services
Docker, GitHub Actions, CI/CD, dev/stage environments, Scrum, code review
Observability: Grafana/Prometheus, profiling, performance analysis
Languages: English – B2, Ukrainian – Native
Certifications: AWS Cloud Practitioner – 2024, Spring Framework Certification – 2023

EXPERIENCE
MedTech Solutions, Java Backend Developer Sep 2024 – Present | Remote
Built backend for a multi-tenant medical platform used by doctors, admins, and ops teams.
Worked in domain-oriented microservices with org–facility–department hierarchy and PBAC.
Contributed to architecture decisions within scope; improved security, GDPR controls, and DB speed.
Designed REST APIs (10–20 endpoints/service) covering core workflows and CRUD scenarios.
Implemented PBAC/RBAC with policy/specification patterns to enforce org-hierarchy permissions.
Applied DDD-lite layering (controller/service/repo) with DTO+Mapper for stable API contracts.
Delivered GDPR controls: access logs, data minimization, log masking, retention, encryption.
Secured auth with JWT access/refresh in HTTP-only cookies plus 2FA via phone/email triggers.
Optimized PostgreSQL joins and ORM N+1 via composite/partial indexes, fetch joins, aggregates.
Reduced complex relationship query time from ~5–10s to <1–2s via indexing and query redesign.
Integrated external DICOM viewer service; enabled streaming and transfer limits for large data.
Improved SLA via stateless services, optimized DB access, centralized errors, and API validation.
Tech Stack: Java, Spring Boot, REST, PostgreSQL, JPA/Hibernate, JWT, RBAC/ABAC, Scrum
Independent Contractor, Java Backend Developer Jun 2023–Aug 2024 | Remote
Progressed from junior module delivery to owning backend blocks end-to-end in a MedTech startup.
Worked across monolith and microservices, building APIs, real-time flows, integrations, and security.
Increased architectural ownership: service boundaries, API contracts, DB optimization, and reviews.
Delivered CRUD modules, integrations, and bug fixes under mentoring in early-stage projects.
Owned functional backend blocks end-to-end: API design, integrations, DB tuning, and reviews.
Built REST-based service communication; used WebSocket for real-time and Kafka for async flows.
Improved real-time stability under bursts via Kafka buffering, Redis caching, retries, back-pressure.
Optimized PostgreSQL read latency with JOIN tuning, composite/partial indexes, and JPA tuning.
Used MongoDB for document-like or loosely structured data alongside PostgreSQL core storage.
Implemented JWT auth (access/refresh via HTTP-only cookies) plus RBAC/ABAC and audit logs.
Integrated AWS S3, external REST APIs, SMS/email providers, and Python ML services with retries.
Maintained Docker + GitHub Actions pipelines for build, tests, and deploy across dev/stage envs.
Tech Stack: Java, Spring Boot, REST, WebSocket, Kafka, Redis, PostgreSQL, MongoDB, JPA, JWT, Docker, GitHub