Leni

Senior Full-Stack Engineer

Not Applicable • Freelance

Jun 2024 - Present • 1 yr 11 mos

● Built core exam services in Kotlin (Spring Boot/Ktor) delivering randomized question pools, time-boxed sessions, scoring, and detailed feedback across multiple vehicle categories (car, motorcycle, etc.). Designed a clean, extensible domain model for questions/answers/media with versioning and tagging to enable continuous content updates and multi-language support. Implemented progress tracking and analytics (attempt history, weak-area heatmaps) to improve learner outcomes and guide content improvements. Boosted performance and reliability through Kotlin coroutines, caching (e.g., Redis), idempotent APIs, plus strong validation and rate limiting to handle high-traffic exam windows. ● Provided virtual assistance for Wix and WordPress websites, supporting day-to-day site updates, page builds, and content publishing to keep client sites clean, accurate, and up to date. Managed layout and formatting, uploaded and optimized images, updated menus and basic SEO fields (titles, meta descriptions, slugs), and ensured mobile responsiveness across pages. Assisted with plugin/theme updates, troubleshooting common site issues, and coordinating revisions based on client feedback—helping deliver polished, user-friendly websites on schedule. ● Developed blockchain applications on Solana using Rust, building and maintaining on-chain programs (smart contracts) with a focus on security, performance, and clean architecture. Implemented core features such as account/state management, instruction handling, and transaction validation, and integrated programs with client-side apps using Solana/Web3 tooling. Added thorough testing, error handling, and upgrade-friendly patterns, while collaborating with stakeholders to translate product requirements into reliable on-chain and off-chain components suitable for production deployments.

Senior Full-Stack Engineer

Encora • Período integral

Jun 2024 - Sep 2025 • 1 yr 3 mos

● Designed and delivered an offline-first payments platform using Java + Spring on AWS, enabling secure NFC tap-to-pay, QR, and wearable/watch pay in low/no connectivity via local queues, idempotency, and eventual consistency. ● Integrated Google Pay and Alipay (plus other global schemes) with tokenization, device binding, and risk controls; added face/biometric (“smile to pay”) checkout while adhering to regional security and compliance standards. ● Built scalable microservices with clear REST APIs, retries, and observability (tracing/metrics/logging) to ensure reliable authorizations and settlements; provided partner SDKs/APIs for rapid merchant onboarding and operations.

Full Stack Engineer

Collabera • Freelance

Jun 2022 - May 2024 • 1 yr 11 mos

● Travel Booking Platform: Built RESTful backend services using Java, Spring Boot, and MySQL to support reservations, payments, and itinerary management; implemented clean API contracts, error handling, and unit/integration tests. ● Banking Application: Developed SOA- and microservices-based components with Java, Spring Boot, and Maven, enabling modular deployments, clearer service boundaries, and easier scalability across core banking workflows. ● Medical Reimbursement System: Designed and implemented a microservices architecture to streamline reimbursement submission, review, and approval workflows; introduced messaging and API gateways to improve maintainability and throughput.