Multi-Source Data Access with Cube.js
A Cube.js semantic layer that gives backend services one clear interface for reading and joining data from multiple data sources at runtime.
Cube.jsGraphQLRESTSQLCaching
Backend & architecture · Available remotely
Senior Java Backend Engineer
Microservices · Kafka · Spring/Quarkus · Cloud · AI/LLM
Dmytro Onyshchenko
Helping turn ideas into production-ready systems.
- 9+ years
- Backend & architecture
- E-commerce · Logistics · IoT · SaaS
Engineer.javatyping…
1Technologies I work with
Java
Quarkus
Spring
Kafka
Postgres
Oracle
Node.js
Azure
AWS
Docker
Kubernetes
ClaudeJavaQuarkusSpringKafkaPostgresOracleNode.jsAzureAWSDockerKubernetesClaude- Java
- Quarkus
- Spring
- Kafka
- Postgres
- Oracle
- Node.js
- Azure
- AWS
- Docker
- Kubernetes
- Claude
Toolbox
Skills
I focus on backend systems and architecture: microservices, event-driven designs, and the operational discipline that keeps high-load products reliable. Domains I know well include e-commerce and industrial IoT / climate solutions.
Architecture
- Microservices
- Event-driven architecture
- DDD
- Multi-tenant SaaS
Backend
- Java 11+
- Quarkus
- Spring Boot
Hibernate- jOOQ
REST
Messaging
- Kafka
RabbitMQ
Databases
- PostgreSQL
- Oracle DB
MongoDB
Redis- DynamoDB
Cloud & DevOps
- Docker
- Kubernetes
- Azure
- AWS
Argo- Azure Pipelines
GitHub Actions
Leadership
- Technical leadership
- Mentoring
- Code reviews
- Hiring
- Onboarding
AI & LLM
LangChain4j- OpenAI APIs
- LLM agents
MCP
Certifications
- ClaudeArchitect – FoundationsMay 2026
- MicrosoftAzure AI FundamentalsJun 2024
- AWSCertified Developer – AssociateApr 2022
Languages
- EnglishWorking proficiency
- UkrainianNative
Master’s in Industrial Machinery Engineering, Kyiv Polytechnic Institute, graduated 2019
Career
Experience
Tech Lead with 9+ years of experience in backend development and system design. Proven in leading engineering teams, designing scalable microservice architectures, and delivering high-load systems in e-commerce and IoT domains. Strong focus on technical leadership, architectural decision-making, and close collaboration with product and business stakeholders.
Dec 2017 – Present · each tick is one month
- SeniorLeadMay 2023 – Present· 3 yrs 5 mos
Industrial IoT & climate solutions
An industrial machinery business that engineers energy-efficient heating and cooling products and solutions for buildings, industry, infrastructure, and the food cold chain, with about 11,300 employees worldwide and €3.1bn in net sales. Latest work centers on a multi-tenant SaaS platform (via EPAM Systems engagement).
- Led backend performance optimization across multiple microservices, reducing average API latency by 35% through profiling, database tuning, and caching strategies.
- Managed production on-call and incident resolution across multiple backend services, reducing MTTR by 30% through improved alerting, runbooks, and root cause analysis.
- Designed and evolved architecture across microservices, authoring ADRs covering service boundaries, API contracts, event-driven communication, and scalability decisions.
- SeniorAug 2021 – May 2023· 1 yr 9 mos
E-commerce & cloud
A global e-commerce, cloud computing, and consumer technology company that operates online retail and related services.
- Built and operated cloud workloads on AWS, owning infrastructure setup, application maintenance, and production support across EC2, RDS, S3, Lambda, and CloudWatch.
- Designed and implemented new microservices end-to-end, covering service architecture, API development, AWS integration, deployment, and production support, enabling independent service deployment and evolution.
- Designed and implemented DynamoDB single-table data models, defining access patterns, partition and sort key strategies, and indexes to support scalable and performant data access.
- JuniorAssociateSeniorDec 2017 – Aug 2021· 3 yrs 8 mos
Global logistics
A global transportation and logistics company that provides parcel delivery, e-commerce shipping and fulfillment, express, and multimodal freight plus supply chain management, with 10,000+ employees worldwide.
- Integrated backend systems with 2 major digital wallet platforms, delivering Apple Wallet and Google Wallet integrations for digital pass issuance, updates, and lifecycle management.
- Resolved production incidents and supported backend applications, troubleshooting functional and technical issues and driving root-cause analysis to improve application stability.
- Proposed and implemented technical solutions for business requirements, delivering 10+ backend features end-to-end from technical design and API development through testing, deployment, and production support.
Portfolio
Case studies
Open a card for the full write-up with architecture diagrams.
Public API Platform
A public, tenant-aware API that lets external clients and vendors read raw telemetry data, secured with Keycloak tokens and fronted by Azure API Management.
KeycloakAzure API ManagementQuarkusOAuth2Java
Remote Connectivity with WireGuard
Secure remote access to on-site controllers and industrial gateways through per-tenant WireGuard tunnels, provisioned with GitOps on Kubernetes.
WireGuardPythonQuarkusKubernetesJava
Configurable Reporting System
A flexible, fault-tolerant reporting platform where users from any tenant create and manage their own reports from the UI, replacing a single-tenant service with a handful of fixed reports.
QuarkusKafkaDebeziumCarbone IOAzure Storage
Trading Accounts Platform
A personal web platform for traders to manage multiple trading and prop-firm accounts in one place, with position analysis, custom trading rules and dashboards.
QuarkusReactTypeScriptPostgreSQLIntegrations
Telegram Bot and Mini App for Fitness Coaches
A Telegram bot and Mini App where fitness coaches manage trainees, programs and sessions, and trainees follow their plans, with AI-assisted program entry and a freemium subscription model.
TelegramQuarkusReactPostgreSQLGoogle Gemini
These are only a selection of my latest case studies. Want to discuss them in more detail or have questions? Get in touch.
About Me
Life beyond the keyboard
Away from work I try to live at a human pace. I am a senior engineer by craft, but I care just as much about staying healthy, curious, and close to the people I love. Active rest is how I reset — not scrolling, but moving.
I love the outdoors: mountain hiking, long trails, and camping under open skies. Packing a backpack, finding a quiet path, and falling asleep to wind and water clears my head after weeks of systems, incidents, and delivery pressure. Those trips remind me that progress is not only shipped in code.
I am a runner, too. Training for distance taught me patience and consistency — the same habits that help in engineering. Completing my first marathon was a personal milestone I am very proud of: months of early runs, race-day nerves, and a finish that still makes me smile whenever I think about it.
Family time is non-negotiable. Whether it is a quiet evening at home, a shared weekend, or an outdoor day everyone can enjoy, I want my calendar to leave room for the people closest to me — not only for trails and finish lines. Being present with family keeps me grounded and makes the hard days of work worth it.
In short, I try to balance deep technical work with a life that feels full: mountains, miles, and moments with family. That mix keeps me energized, focused, and ready for the next challenge.
Hiking
Contact
Let’s talk
Always glad to talk about backend systems, architecture, and the problems behind them. If you are building something and want a collaborator, a second opinion, or a team member, say hello.
Email
LinkedIn
linkedin.com/in/dmytro-onys
Send a message
A short note on role, timeline, or engagement scope is enough.