Hendrik R.
Full Stack Developer
Experience
May 2021 - Present
4 years 8 monthsFull Stack Developer
Mainmatter
- Designed and delivered Spring Boot microservices with clean architecture and JPA, exposing versioned REST and GraphQL endpoints with pagination, filtering, and standardized error envelopes that reduced client-side defects and support load.
- Implemented OAuth2/JWT with Spring Security and method-level authorization, enabling least-privilege access while keeping session management robust with refresh token rotation and CSRF/CORS hardening.
- Optimized hot database paths using query hints, indexed search, and Hibernate second-level caching, cutting P95 latency and stabilizing throughput under peak traffic.
- Built WebSocket/SSE channels for real-time notifications and workflow progress, replacing polling and reducing backend compute while increasing UI freshness.
- Created batch and ETL pipelines with Spring Batch to ingest third-party data and normalize it into reporting stores, powering dashboards and time-series analysis with Elasticsearch and PostgreSQL.
- Introduced contract testing and schema evolution practices for APIs, enabling backward-compatible changes and safe incremental front-end rollouts.
- Instrumented services with structured logging and OpenTelemetry traces/metrics, improving root-cause analysis and reducing MTTR across incidents.
- Containerized Java services with Docker and deployed to Kubernetes with GitHub Actions, implementing blue-green rollouts, health probes, and automated database migration gates.
- Enforced quality with JUnit 5/Mockito/Testcontainers for service layers and Selenium for critical flows, gating releases with CI coverage thresholds and smoke suites.
- Mentored engineers on Spring patterns (transaction boundaries, DTO mapping, validation) and performance profiling with JFR/Async Profiler to remove allocation hotspots and N+1 queries.
Feb 2017 - Apr 2021
4 years 3 monthsFull Stack Developer
EMPIST
- Delivered Spring Boot APIs for e-commerce and B2B portals, standardizing DTOs, pagination contracts, and problem-details errors that simplified SPA consumption and reduced integration churn.
- Implemented Identity and Access Management with Spring Security, OAuth2/OIDC, and SAML SSO, aligning RBAC policies across admin and customer applications.
- Built ETL jobs in Java to aggregate data from partner APIs into Elasticsearch and PostgreSQL, enabling fast search, facets, and KPI reporting for business stakeholders.
- Improved performance with compiled JPA queries, batch writes, and connection-pool tuning, lowering CPU utilization and improving P95/P99 across peak periods.
- Added real-time capabilities via WebSocket endpoints and durable subscriptions, keeping inventory, notifications, and activity feeds synchronized without client polling.
- Established automated testing with JUnit/Mockito for services and Selenium for checkout and subscription journeys, introducing CI pipelines with artifact versioning and feature-flagged releases.
- Applied accessibility and SEO requirements by coordinating server-rendered content where needed and aligning API shapes to front-end state models to reduce over-fetching.
- Introduced observability with correlation IDs, structured logs, and performance budgets, enabling proactive capacity planning and faster incident triage.
- Refactored legacy controllers into layered services and repository patterns, improving cohesion, testability, and onboarding speed for new engineers.
- Collaborated with product and UX to define API acceptance criteria and telemetry events, prioritizing features that measurably improved conversion and retention.
Jul 2014 - Jan 2017
2 years 7 monthsFrontend Developer
First Line Software
- Built production UIs that consumed Java Spring Web API services, adding resilient HTTP client layers with retry, cancellation, and typed contracts to stabilize data-heavy views.
- Progressively introduced TypeScript in 2016 and planned a staged migration to modern SPA patterns, reducing runtime defects and improving developer feedback cycles.
- Created a reusable component library and documented integration patterns against Spring endpoints, accelerating delivery and ensuring visual consistency across teams.
- Implemented accessible forms and error states aligned with ARIA/WCAG, increasing task completion rates and reducing support tickets.
- Optimized asset delivery with async loading and early code-splitting aligned to API caching semantics, improving first paint and interactive metrics.
- Added targeted unit and integration tests around high-risk components and API adapters, catching regressions earlier and shortening review cycles.
- Partnered with backend engineers to refine Java API contracts, remove N+1 patterns, and provide consistent error semantics that simplified client error handling.
Summary
Senior software engineer specializing in Java and Spring Boot who designs secure, scalable APIs and data platforms that power fast, accessible web applications across healthcare, e-commerce, and fintech.
Expert in Spring Boot microservices, Spring Security/OAuth2/JWT, and CI-driven quality with JUnit/Mockito that improves reliability, lowers P95 latency, and accelerates delivery in complex data-heavy systems.
Product-minded partner who builds accessible UIs with modern front ends, instruments analytics/A-B tests for evidence-based iteration, and optimizes cloud costs while maintaining performance at scale.
Languages
English
AdvancedEducation
Oct 2010 - Jun 2014
Vrije Universiteit Amsterdam
Bachelor’s degree · Computer Science · Amsterdam, Netherlands
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