Mariusz Wekwejt

Delivered new React/Next.js workflows integrated with Node.js APIs, reducing multi-step manual operations into guided UI flows and cutting average task completion time for target processes by ~30% (measured via in-app event timings).

Designed versioned REST endpoints and validation layers for Node.js services; reduced client-breaking changes by introducing OpenAPI-driven reviews and backward-compatible rollout patterns.

Improved API latency on key endpoints (p95) by introducing Redis caching and PostgreSQL query/index tuning, lowering p95 from ~420ms to ~210ms (measured in Grafana dashboards).

Added Jest unit coverage and Playwright smoke suites for critical user journeys; reduced regression escapes by shifting checks into PR gating and nightly runs.

Implemented baseline observability with OpenTelemetry traces and structured logs across services; cut incident triage time from ~55 minutes to ~25 minutes by correlating traces with request IDs across UI/API.

Built and shipped React components and state management patterns for data-heavy screens, improving perceived UI responsiveness by optimizing rendering and API pagination (measured via browser performance traces).

Developed Node.js (TypeScript) REST APIs with consistent error contracts and idempotency for write operations, reducing duplicate-write incidents in production.

Modernized legacy Java/Spring Boot modules by extracting business logic into testable services and adding integration tests; reduced production hotfixes by ~20% over two quarters (release notes + incident counts).

Introduced Jest + contract-like API tests to prevent breaking changes between UI and backend; reduced rollback events from 3 in one quarter to 1 in the next.

Implemented security improvements: input validation, rate limiting on sensitive endpoints, and dependency vulnerability remediation; aligned changes with OWASP guidance and internal security review checklists.

Designed and implemented Spring Boot microservices with clear domain boundaries and API contracts, improving maintainability and reducing cross-service coupling during feature work.

Improved throughput for high-traffic endpoints by optimizing SQL queries and adding Redis caching for hot reads; reduced database load and improved p95 response times (measured in Prometheus/Grafana).

Strengthened reliability by adding health checks, circuit-breaking patterns where applicable, and better timeout/retry defaults; reduced incident frequency tied to downstream slowness.

Built CI pipelines (Jenkins) with automated unit/integration tests and container builds; shortened “merge to deployable artifact” time by standardizing pipeline stages.

Added structured logging and key service-level dashboards (error rate, latency, saturation) to speed up production debugging and improve on-call handoffs.

Developed web features across server-rendered and SPA-adjacent front-ends, integrating UI flows with REST endpoints and ensuring consistent validation and error handling.

Implemented data access layers with Hibernate/JPA, reducing recurring performance issues by addressing N+1 queries and adding indexes for top access paths.

Increased release confidence by expanding JUnit coverage for service logic and adding integration tests for critical API paths.

Contributed to code reviews and refactoring initiatives to improve readability, modularity, and long-term change safety.