Bogdan Bak
Senior Full Stack Engineer
Experience
Senior Full Stack Engineer
Makolab
- Led architecture for a multi-tenant eCommerce SaaS that powers branded storefronts and headless experiences across regions.
- Defined service boundaries and interfaces while migrating microservices from Ruby on Rails to Node.js (NestJS), reducing cold-start latency and simplifying deployment pipelines.
- Built new React and Next.js frontends with server-side rendering and static generation; improved Core Web Vitals and decreased LCP by double-digit percentages.
- Delivered Shopify embedded app integrations using OAuth, App Bridge, Polaris UI, and webhooks for orders, inventory, and fulfillment.
- Implemented WordPress as content hub (headless mode), exposing GraphQL and REST endpoints consumed by Next.js storefronts.
- Designed internal GraphQL gateway and versioned REST APIs with OpenAPI, enabling partner integrations and third-party marketplaces.
- Introduced AI features: product recommendation service and semantic search using Python (FastAPI) plus vector search; integrated OpenAI for copy suggestions, FAQs, and support triage.
- Wrote small utilities in Go for log processing and concurrent sitemap generation to speed up SEO jobs.
- Shipped mobile features with React Native, reusing TypeScript business logic and API clients from web packages.
- Implemented background processing with Sidekiq (Rails legacy) and BullMQ (Node), including idempotency keys and dead-letter queues.
- Built real-time order status channels with WebSockets and server-sent events to keep dashboards and kiosks in sync.
- Hardened security: OAuth 2.0, OIDC, signed webhooks, HMAC validation, rate limiting, secrets rotation on AWS Secrets Manager.
- Owned CI/CD on GitHub Actions and GitLab CI: multi-stage Docker builds, preview environments, Terraform modules, and automated schema checks.
- Established testing strategy: unit tests (Jest, RSpec), component tests (React Testing Library), end-to-end (Cypress), and contract tests (Pact) between services.
- Tuned PostgreSQL and Redis caching; created read models and projections for analytics; added ElasticSearch for catalog faceting.
- Set up observability: Prometheus metrics, Datadog traces, structured logs, error budgets, and SLO dashboards for critical endpoints.
- Collaborated with product, design, and merchants; translated requirements into technical roadmaps and capacity plans.
- Mentored engineers on code reviews, API consistency, performance profiling, and incident response.
Full-Stack Engineer
IXOPAY
- Contributed to a fintech transaction platform focused on high throughput, reliability, and compliance.
- Migrated customer-facing frontend from Angular to React, introducing TypeScript, hooks, and shared UI kits.
- Built Node.js microservices for transaction routing, settlement exports, and provider webhooks; integrated Laravel and Ruby on Rails legacy endpoints during the transition.
- Implemented real-time notifications for payment status with WebSockets and server-sent events, improving operations dashboards.
- Added AI/ML components in Python for anomaly and fraud detection; produced features from transaction graphs and trained baseline models to alert risk teams.
- Designed idempotent webhooks and reconciliation jobs; improved data quality and rerun safety for payment providers.
- Tuned PostgreSQL indices, optimized Redis patterns for ephemeral state, and reduced P95 latencies across several APIs.
- Automated deployments on AWS (ECS, Lambda, API Gateway, S3) with infrastructure as code and blue-green rollouts.
- Strengthened authentication and authorization flows with OAuth 2.0 and JSONWeb Tokens; added audit trails.
- Expanded test coverage with Jest, Cypress, and Postman collections; added health checks, circuit breakers, and dashboards for on-call.
Web Developer
Fabrique
- Built healthcare and hospitality web projects from greenfield to launch with WordPress, Shopify, Ruby, and SQL backends.
- Developed responsive frontend features and pages in React and vanilla JavaScript; implemented accessible components and forms.
- Created backend endpoints for bookings, patient content workflows, and inventory; integrated with external APIs for payments and email.
- Wrote custom Shopify themes and Liquid sections; synchronized catalog and pricing with back-office systems via Admin API.
- Implemented search and faceting with ElasticSearch; added server-side caching and HTTP caching strategies.
- Optimized database queries with proper indexing and pagination; reduced heavy endpoints’ response times.
- Added automated tests with PHPUnit and Jest; established basic CI pipelines for builds and linting.
- Collaborated with designers and editors to ship performance-focused pages and content workflows.
Industries Experience
See where this freelancer has spent most of their professional time. Longer bars indicate deeper hands-on experience, while shorter ones reflect targeted or project-based work.
Experienced in Information Technology (4 years), Retail (4 years), Healthcare (3.5 years), Tourism (3.5 years), and Banking and Finance (2.5 years).
Business Areas Experience
The graph below provides a cumulative view of the freelancer's experience across multiple business areas, calculated from completed and active engagements. It highlights the areas where the freelancer has most frequently contributed to planning, execution, and delivery of business outcomes.
Experienced in Information Technology (10.5 years), Product Development (10.5 years), and Quality Assurance (2.5 years).
Summary
Senior Full-Stack Software Engineer specializing in Ruby on Rails, Node.js, React, and Shopify applications. 10 years experience building eCommerce, fintech, and SaaS platforms end-to-end, from architecture and microservices to polished frontends and CI/CD in the cloud. Comfortable leading squads, designing APIs, and shipping reliable features with automated tests. Hands-on with AI and machine learning integrations for recommendations, search, and fraud detection. Strong DevOps mindset on Amazon Web Services with infrastructure as code, observability, and cost awareness. Passionate about clean code, performance, and developer experience.
Skills
Frontend: React, Next.js, Redux/zustand, React Query, React Native, Typescript/javascript, Html5, Css3, Scss, Tailwind Css, Material Ui, Shopify, Liquid, Webpack, Vite, Storybook, Accessibility/web Vitals, Wordpress
Backend: Ruby On Rails, Php (Laravel), Node.js (Express, Nestjs), Graphql, Rest Api Design, Webhooks, Grpc, Websockets, Server-sent Events, Sidekiq, Bullmq, Event-driven And Microservices Patterns, Domain-driven Design, Oauth 2.0, Openid Connect, Jsonweb Tokens
Databases: Postgresql, Mysql, Mongodb, Redis, Elasticsearch, Sqlite, Kafka/rabbitmq
Ai & Data: Python (Fastapi, Scikit-learn), Openai Api, Vector Search (Faiss, Pinecone), Embeddings And Rag Patterns, Golang
Devops & Tools: Aws (Ecs, Eks, Lambda, Api Gateway, S3, Cloudfront, Rds, Dynamodb, Cloudwatch), Docker, Kubernetes, Terraform, Github Actions, Gitlab Ci, Jenkins, Argo Cd, Feature Flags, Launchdarkly, Prometheus, Grafana, Datadog, Sentry
Testing & Quality: Rspec, Minitest, Jest, React Testing Library, Cypress, Playwright, Pact, Testcontainers, Postman, Tdd/ci-gated Quality Thresholds
Languages
Education
Delft University of Technology
Bachelor of Computer Science · Computer Science · Delft, Netherlands
Profile
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